.\" Hey, Emacs, edit this file in -*- nroff-fill -*- mode .\" .Dd 15 January 1999 .Dt vinum 8 .Sh NAME .Nm vinum .Nd Logical Volume Manager control program .Sh SYNOPSIS .Nm .Op command .Op Fl options .Sh COMMANDS .Cd create .Fl f .Ar description-file .in +1i Create a volume as described in .Ar description-file .in .\" XXX remove this .Cd attach Ar plex Ar volume .Op Nm rename .Cd attach Ar subdisk Ar plex Ar [offset] .Op Nm rename .in +1i Attach a plex to a volume, or a subdisk to a plex. .in .\" XXX remove this .Cd debug .in +1i Cause the volume manager to enter the kernel debugger. .in .Cd debug .Ar flags .in +1i Set debugging flags. .in .Cd detach .Op Ar plex | subdisk .in +1i Detach a plex or subdisk from the volume or plex to which it is attached. .in .Cd info .Op Fl v .in +1i List information about volume manager state. .in .Cd init .Op Fl v .in +1i .\" XXX Initialize a plex by writing zeroes to all its subdisks. .in .Cd label .Ar volume .in +1i Create a volume label .in .Cd list .Op Fl r .Op Fl s .Op Fl v .Op Fl V .Op volume | plex | subdisk .in +1i List information about specified objects .in .Cd l .Op Fl r .Op Fl s .Op Fl v .Op Fl V .Op volume | plex | subdisk .in +1i List information about specified objects (alternative to .Cd list command) .in .Cd ld .Op Fl r .Op Fl s .Op Fl v .Op Fl V .Op volume .in +1i List information about drives .in .Cd ls .Op Fl r .Op Fl s .Op Fl v .Op Fl V .Op subdisk .in +1i List information about subdisks .in .Cd lp .Op Fl r .Op Fl s .Op Fl v .Op Fl V .Op plex .in +1i List information about plexes .in .Cd lv .Op Fl r .Op Fl s .Op Fl v .Op Fl V .Op volume .in +1i List information about volumes .in .Cd printconfig .Pa file .in +1i Write a copy of the current configuration to .Pa file . .in .Cd makedev .in +1i Remake the device nodes in .Ar /dev/vinum . .in .Cd quit .in +1i Exit the .Nm program when running in interactive mode. Normally this would be done by entering the .Ar EOF character. .in .Cd read .Ar disk Op disk... .in +1i Read the .Nm configuration from the specified disks. .in .Cd rename Op Fl r .Ar [ drive | subdisk | plex | volume ] .Ar newname .in +1i Change the name of the specified object. .ig XXX .in .Cd replace .Ar [ subdisk | plex ] .Ar newobject .in +1i Replace the object with an identical other object. XXX not implemented yet. .. .in .Cd resetconfig .in +1i Reset the complete .Nm configuration. .in .Cd resetstats .Op Fl r .Op volume | plex | subdisk .in +1i Reset statistisc counters for the specified objects, or for all objects if none are specified. .in .Cd rm .Op Fl f .Op Fl r .Ar volume | plex | subdisk .in +1i Remove an object .in .Cd saveconfig .in +1i Save .Nm configuration to disk. .in .ig XXX .Cd set .Op Fl f .Ar state .Ar volume | plex | subdisk | disk .in +1i Set the state of the object to \fIstate\fP\| .in .. .Cd setdaemon .Op value .in +1i Set dæmon configuration. .in .Cd start .Op volume | plex | subdisk .in +1i Allow the system to access the objects .in .Cd stop .Op Fl f .Op volume | plex | subdisk .in +1i Terminate access to the objects, or stop .Nm if no parameters are specified. .in .Sh DESCRIPTION .Nm is a utility program to communicate with the \fBVinum\fP\| logical volume manager. See .Xr vinum 4 for more information about the volume manager. .Xr vinum 8 is designed either for interactive use, when started without a command, or to execute a single command if the command is supplied as arguments to .Nm vinum . In interactive mode, .Nm maintains a command line history. .Ss OPTIONS .Nm commands may optionally be followed by an option. Any of the following options may be specified with any command, but in some cases they do not make any difference: cases, the options are ignored. For example, the .Nm stop command ignores the .Fl v and .Fl V options. .Bl -hang .It Cd -v The .Nm -v option can be used with any command to request more detailed information. .It Cd -V The .Nm -V option can be used with any command to request more detailed information than the .Nm -v option provides. .It Cd -f The .Nm -f option overrides safety checks. Use with extreme care. This option is for emergency use only. For example, the command .Bd -unfilled -offset indent rm -f myvolume .Ed .Pp removes .Nm myvolume even if it is open. Any subsequent access to the volume will almost certainly cause a panic. .It Cd -r The .Nm -r .if t (``recursive'') .if n ("recursive") option is used by the list commands to display information not only about the specified objects, but also about subordinate objects. For example, in conjnction with the .Nm lv command, the .Nm -r option will also show information about the plexes and subdisks belonging to the volume. .It Cd -s The .Nm -s option is used by the list commands to display statistical information. .El .Pp .Ss COMMANDS IN DETAIL .Pp .Nm commands perform the following functions: .Bl -hang .It Nm attach Ar plex Ar volume .Op Nm rename .if n .sp -1v .if t .sp -.6v .It Nm attach Ar subdisk Ar plex Ar [offset] .Op Nm rename .sp .Nm .Ar attach inserts the specified plex or subdisk in a volume or plex. In the case of a subdisk, an offset in the plex may be specified. If it is not, the subdisk will be attached at the first possible location. After attaching a plex to a non-empty volume, .Nm reintegrates the plex. .Pp If the keyword .Nm rename is specified, .Nm renames the object (and in the case of a plex, any subordinate subdisks) to fit in with the default .Nm naming convention. .Pp A number of considerations apply to attaching subdisks: .Bl -bullet .It Subdisks can normally only be attached to concatenated plexes. .It If a striped or RAID-5 plex is missing a subdisk (for example after drive failure), it may be replaced by a subdisk of the same size only. No other attachment of subdisks is currently allowed. .It For concatenated plexes, the .Ar offset parameter specifies the offset in blocks from the beginning of the plex. For striped and RAID-5 plexes, it specifies the offset of the first block of the subdisk: in other words, the offset is the numerical position of the subdisk multiplied by the stripe size. For example, in a plex of block size 256k, the first subdisk will have offset 0, the second offset 256k, the third 512k, etc. This calculation ignores parity blocks in RAID-5 plexes. .El .It Nm create Fl f Ar description-file .sp .Nm .Ar create is used to create any object. In view of the relatively complicated relationship and the potential dangers involved in creating a .Nm object, there is no interactive interface to this function. See the section CONFIGURATION FILE below for more information. .Pp Note that the .Nm .Ar create function is additive: if you run it multiple times, you will create multiple copies of all unnamed objects. .Pp Normally the .Nm create command will not change the names of existing .Nm drives, in order to avoid accidentally erasing them. The correct way to dispose of no longer wanted .Nm drives is to reset the configuration with the .Nm resetconfig command. In some cases, however, it may be necessary to create new data on .Nm drives which can no longer be started. In this case, use the .Nm create Fl f command. .It Nm debug .Pp .Nm .Ar debug is used to enter the remote kernel debugger. It is only activated if .Nm is built with the .Ar VINUMDEBUG option. This option will stop the execution of the operating system until the kernel debugger is exited. If remote debugging is set and there is no remote connection for a kernel debugger, it will be necessary to reset the system and reboot in order to leave the debugger. .It Nm debug .Ar flags .Pp Set a bit mask of internal debugging flags. These will change without warning as the product matures; to be certain, read the header file .Pa sys/dev/vinumvar.h . The bit mask is composed of the following values: .Bl -hang .It DEBUG_ADDRESSES (1) .br Show buffer information during requests .It DEBUG_NUMOUTPUT (2) .br Show the value of .Dv vp->v_numoutput. .It DEBUG_RESID (4) .br Go into debugger in .Fd complete_rqe. .It DEBUG_LASTREQS (8) .br Keep a circular buffer of last requests. .It DEBUG_REVIVECONFLICT (16) .br Print info about revive conflicts. .It DEBUG_EOFINFO (32) .br Print information about internal state when returning an EOF on a striped plex. .It DEBUG_MEMFREE (64) .br Maintain a circular list of the last memory areas freed by the memory allocator. .It DEBUG_REMOTEGDB (256) .br Go into remote .Ic gdb when the .Nm debug command is issued. .El .It Nm detach Op Fl f .Ar plex .if n .sp -1v .if t .sp -.6v .It Nm detach Op Fl f .Ar subdisk .sp .Nm .Ar detach removes the specified plex or subdisk from the volume or plex to which it is attached. If removing the object would impair the data integrity of the volume, the operation will fail unless the .Fl f option is specified. If the object is named after the object above it (for example, subdisk vol1.p7.s0 attached to plex vol1.p7), the name will be changed by prepending the text .if t ``ex-'' .if n "ex-" (for example, ex-vol1.p7.s0). If necessary, the name will be truncated in the process. .Pp .Nm detach does not reduce the number of subdisks in a striped or RAID-5 plex. Instead, the subdisk is marked absent, and can later be replaced with the .Nm attach command. .It Nm info .br .Nm .Ar info displays information about .Nm memory usage. This is intended primarily for debugging. With the .Fl v option, it will give detailed information about the memory areas in use. .Pp With the .Fl V option, .Ar info displays information about the last up to 64 I/O requests handled by the .Nm driver. This information is only collected if debug flag 8 is set. The format looks like: .Pp .Bd -literal vinum -> info -V Flags: 0x200 1 opens Total of 38 blocks malloced, total memory: 16460 Maximum allocs: 56, malloc table at 0xf0f72dbc Time Event Buf Dev Offset Bytes SD SDoff Doffset Goffset 14:40:00.637758 1VS Write 0xf2361f40 0x5b03 0x10 16384 14:40:00.639280 2LR Write 0xf2361f40 0x5b03 0x10 16384 14:40:00.639294 3RQ Read 0xf2361f40 0x427 0x104109 8192 19 0 0 0 14:40:00.639455 3RQ Read 0xf2361f40 0x417 0xd2109 8192 17 0 0 0 14:40:00.639529 3RQ Read 0xf2361f40 0x40f 0x6e109 8192 16 0 0 0 14:40:00.652978 4DN Read 0xf2361f40 0x427 0x104109 8192 19 0 0 0 14:40:00.667040 4DN Read 0xf2361f40 0x40f 0x6e109 8192 16 0 0 0 14:40:00.668556 4DN Read 0xf2361f40 0x417 0xd2109 8192 17 0 0 0 14:40:00.669777 6RP Write 0xf2361f40 0x427 0x104109 8192 19 0 0 0 14:40:00.685547 4DN Write 0xf2361f40 0x427 0x104109 8192 19 0 0 0 .Ed .Pp The .Ar Buf field always contains the address of the user buffer header. This can be used to identify the requests associated with a user request, though this is not 100% reliable: theoretically two requests in sequence could use the same buffer header, though this is not common. The beginning of a request can be identified by the event .Ar 1VS . The example above shows the requests involved in a single user request. .Pp The .Ar Event field contains information related to the sequence of events in the request chain. The digit .Ar 1 to .Ar 6 indicates the approximate sequence of events, and the two-letter abbreviation is a mnemonic for the location .Bl -hang .It 1VS (vinumstrategy) shows information about the user request on entry to .Fd vinumstrategy . The device number is the .Nm device, and offset and length are the user parameters. This is always the beginning of a request sequence. .It 2LR (launch_requests) shows the user request just prior to launching the low-level .Nm requests in the function .Fd launch_requests. The parameters should be the same as in the .Ar 1VS information. .Pp In the following requests, .Ar Dev is the device number of the associated disk partition, .Ar Offset is the offset from the beginning of the partition, .Ar SD is the subdisk index in .Dv vinum_conf , .Ar SDoff is the offset from the beginning of the subdisk, .Ar Doffset is the offset of the associated data request, and .Ar Goffset is the offset of the associated group request, where applicable. .It 3RQ (request) shows one of possibly several low-level .Nm requests which are launched to satisfy the high-level request. This information is also logged in .Fd launch_requests. .It 4DN (done) is called from .Fd complete_rqe, showing the completion of a request. This completion should match a request launched either at stage .Ar 4DN from .Fd launch_requests, or from .Fd complete_raid5_write at stage .Ar 5RD or .Ar 6RP . .It 5RD (RAID-5 data) is called from .Fd complete_raid5_write and represents the data written to a RAID-5 data stripe after calculating parity. .It 6RP (RAID-5 parity) is called from .Fd complete_raid5_write and represents the data written to a RAID-5 parity stripe after calculating parity. .El .\" XXX .It Nm init Ar plex .Pp .Nm .Ar init initializes a plex by writing zeroes to all its subdisks. This is the only way to ensure consistent data in a plex. You must perform this initialization before using a RAID-5 plex. It is also recommended for other new plexes. .Pp .Nm initializes all subdisks of a plex in parallel. Since this operation can take a long time, it is performed in the background. .Nm prints a console message when the initialization is complete. .It Nm label .Ar volume .Pp The .Nm label command writes a .Ar ufs style volume label on a volume. It is a simple alternative to an appropriate call to .Ar disklabel . This is needed because some .Ar ufs commands still read the disk to find the label instead of using the correct .Ar ioctl call to access it. .Nm maintains a volume label separately from the volume data, so this command is not needed for .Ar newfs . This command is deprecated. .Pp .It Nm list .Op Fl r .Op Fl V .Op volume | plex | subdisk .if n .sp -1v .if t .sp -.6v .It Nm l .Op Fl r .Op Fl V .Op volume | plex | subdisk .if n .sp -1v .if t .sp -.6v .It Nm ld .Op Fl r .Op Fl s .Op Fl v .Op Fl V .Op volume .if n .sp -1v .if t .sp -.6v .It Nm ls .Op Fl r .Op Fl s .Op Fl v .Op Fl V .Op subdisk .if n .sp -1v .if t .sp -.6v .It Nm lp .Op Fl r .Op Fl s .Op Fl v .Op Fl V .Op plex .if n .sp -1v .if t .sp -.6v .It Nm lv .Op Fl r .Op Fl s .Op Fl v .Op Fl V .Op volume .Pp .Ar list is used to show information about the specified object. If the argument is omitted, information is shown about all objects known to .Nm vinum . The .Ar l command is a synonym for .Ar list . .Pp The .Fl r option relates to volumes and plexes: if specified, it recursively lists information for the subdisks and (for a volume) plexes subordinate to the objects. The commands .Ar lv , .Ar lp , .Ar ls and .Ar ld commands list only volumes, plexes, subdisks and drives respectively. This is particularly useful when used without parameters. .Pp The .Fl s option causes .Nm to output device statistics, the .Op Fl v (verbose) option causes some additional information to be output, and the .Op Fl V causes considerable additional information to be output. .It Nm makedev .br The .Nm makedev command removes the directory /dev/vinum and recreates it with device nodes which reflect the current configuration. This command is not intended for general use, and is provided for emergency use only. .Pp .It Nm quit Exit the .Nm program when running in interactive mode. Normally this would be done by entering the .Ar EOF character. .It Nm printconfig Pa file Write a copy of the current configuration to .Pa file in a format that can be used to recreate the .Nm configuration. Unlike the configuration saved on disk, it includes definitions of the drives. .It Nm read .Ar disk Op disk... .Pp The .Nm read command scans the specified disks for .Nm partitions containing previously created configuration information. It reads the configuration in order from the most recently updated to least recently updated configuration. .Nm maintains an up-to-date copy of all configuration information on each disk partition. You must specify all of the slices in a configuration as the parameter to this command. .Pp The .Nm read command is intended to selectively load a .Nm configuration on a system which has other .Nm partitions. If you want to start all partitions on the system, it is easier to use the .Nm start command. .Pp If .Nm encounters any errors during this command, it will turn off automatic configuration update to avoid corrupting the copies on disk. This will also happen if the configuration on disk indicates a configuration error (for example, subdisks which do not have a valid space specification). You can turn the updates on again with the .Nm setdaemon and .Nm saveconfig commands. Reset bit 4 of the daemon options mask to re-enable configuration saves. .It Nm rename .Op Fl r .Ar [ drive | subdisk | plex | volume ] .Ar newname .Pp Change the name of the specified object. If the .Fl r option is specified, subordinate objects will be named by the default rules: plex names will be formed by appending .p\f(BInumber\fP to the volume name, and subdisk names will be formed by appending .s\f(BInumber\fP to the plex name. .It Nm replace .Ar [ subdisk | plex ] .Ar newobject .Pp Replace the object with an identical other object. This command has not yet been implemented. .It Nm resetconfig .Pp The .Nm resetconfig command completely obliterates the .Nm configuration on a system. Use this command only when you want to completely delete the configuration. .Nm will ask for confirmation: you must type in the words NO FUTURE exactly as shown: .Bd -unfilled -offset indent # \f(CBvinum resetconfig\f(CW WARNING! This command will completely wipe out your vinum configuration. All data will be lost. If you really want to do this, enter the text NO FUTURE Enter text -> \f(BINO FUTURE\fP Vinum configuration obliterated .Ed .ft R .Pp As the message suggests, this is a last-ditch command. Don't use it unless you have an existing configuration which you never want to see again. .It Nm resetstats .Op Fl r .Op volume | plex | subdisk .Pp .Nm maintains a number of statistical counters for each object. See the header file .Fi vinumvar.h for more information. .\" XXX put it in here when it's finalized Use the .Nm resetstats command to reset these counters. In conjunction with the .Fl r option, .Nm also resets the counters of subordinate objects. .It Nm rm .Op Fl f .Op Fl r .Ar volume | plex | subdisk .Pp .Nm rm removes an object from the .Nm configuration. Once an object has been removed, there is no way to recover it. Normally .Nm performs a large amount of consistency checking before removing an object. The .Fl f option tells .Nm to omit this checking and remove the object anyway. Use this option with great care: it can result in total loss of data on a volume. .Pp Normally, .Nm refuses to remove a volume or plex if it has subordinate plexes or subdisks respectively. You can tell .Nm to remove the object anyway by using the .Fl f flag, or you can cause .Nm to remove the subordinate objects as well by using the .Fl r (recursive) flag. If you remove a volume with the .Fl r flag, it will remove both the plexes and the subdisks which belong to the plexes. .It Nm saveconfig .Pp Save the current configuration to disk. This is primarily a maintenance function. For example, if an error occurs on startup, updates will be disabled. When you reenable them, the configuration is not automatically saved to disk. Use this command to save the configuration. .ig .It Nm set .Op Fl f .Ar state .Ar volume | plex | subdisk | disk .Nm set sets the state of the specified object to one of the valid states (see OBJECT STATES below). Normally .Nm performs a large amount of consistency checking before making the change. The .Fl f option tells .Nm to omit this checking and perform the change anyway. Use this option with great care: it can result in total loss of data on a volume. .\"XXX .Nm This command has not yet been implemented. .. .It Nm setdaemon .Op value .Pp .Nm setdaemon sets a variable bitmask for the .Nm dæmon. This command is temporary and will be replaced. Currently, the bit mask may contain the bits 1 (log every action to syslog) and 4 (don't update configuration). Option bit 4 can be useful for error recovery. .It Nm start .Op volume | plex | subdisk .Pp .Nm start starts (brings into to the .Ar up state) one or more .Nm objects. .Pp If no object names are specified, .Nm scans the disks known to the system for .Nm drives and then reads in the configuration as described under the .Nm read commands. The .Nm drive contains a header with all information about the data stored on the drive, including the names of the other drives which are required in order to represent plexes and volumes. .Pp If .Nm encounters any errors during this command, it will turn off automatic configuration update to avoid corrupting the copies on disk. This will also happen if the configuration on disk indicates a configuration error (for example, subdisks which do not have a valid space specification). You can turn the updates on again with the .Nm setdaemon and .Nm saveconfig command. Reset bit 4 of the daemon options mask to re-enable configuration saves. .Pp If object names are specified, .Nm starts them. Normally this operation is only of use with subdisks. The action depends on the current state of the object: .Bl -bullet .It If the object is already in the .Ar up state, .Nm does nothing. .It If the object is a subdisk in the .Ar down or .Ar reborn states, .Nm changes it to the .Ar up state. .It If the object is a subdisk in the .Ar empty state, the change depends on the subdisk. If it is part of a plex which is part of a volume which contains other plexes, .Nm places the subdisk in the .Ar reviving state and attempts to copy the data from the volume. When the operation completes, the subdisk is set into the .Ar up state. If it is part of a plex which is part of a volume which contains no other plexes, or if it is not part of a plex, .Nm brings it into the .Ar up state immediately. .It If the object is a subdisk in the .Ar reviving state, .Nm continues the .Ar revive operation offline. When the operation completes, the subdisk is set into the .Ar up state. .El .Pp When a subdisk comes into the .Ar up state, .Nm automatically checks the state of any plex and volume to which it may belong and changes their state where appropriate. .Pp If the object is a volume or a plex, .Nm start currently has no effect: it checks the state of the subordinate subdisks (and plexes in the case of a volume) and sets the state of the object accordingly. In a later version, this operation will cause the subdisks .Pp To start a plex in a multi-plex volume, the data must be copied from another plex in the volume. Since this frequently takes a long time, it is done in the background. .It Nm stop .Op Fl f .Op volume | plex | subdisk .Pp If no parameters are specified, .Nm stop removes the .Nm kld and stops .Xr vinum 8 . This can only be done if no objects are active, In particular, the .Fl f flag does not override this requirement. This command can only work if .Nm has been loaded as a kld, since it is not possible to unload a statically configured driver, .\" XXX why? and it must be issued at a command prompt: the command .Nm vinum stop will not work. .Nm .Nm stop will fail if .Nm is statically configured. .Pp If object names are specified, .Nm stop disables access to the objects. If the objects have subordinate objects, they subordinate objects must either already be inactive (stopped or in error), or the .Fl r and .Fl f flags must be specified. This command does not remove the objects from the configuration. They can be accessed again after a .Nm start command. .Pp By default, .Nm does not stop active objects. For example, you cannot stop a plex which is attached to an active volume, and you cannot stop a volume which is open. The .Fl f option tells .Nm to omit this checking and remove the object anyway. Use this option with great care and understanding: used incorrectly, it can result in serious data corruption. .El .Ss CONFIGURATION FILE .Nm requires that all parameters to the .Nm create commands must be in a configuration file. Entries in the configuration file define volumes, plexes and subdisks, and may be in free format, except that each entry must be on a single line. .Pp Some configuration file parameters specify a size (lengths, stripe sizes). These lengths can be specified as bytes, as sectors of 512 bytes (by appending the letter \f(CWb\fR), as kilobytes (by appending the letter \f(CWk\fR), as megabytes (by appending the letter \f(CWm\fR) or as gigabytes (by appending the letter \f(CWg\fR). These quantities represent the values 2**10, 2**20 and 2**30 respectively. For example, the value \f(CW16777216\fR bytes can also be written as \f(CW16m\fR, \f(CW16384k\fR or \f(CW32768b\fR. .Pp The configuration file can contain the following entries: .Pp .Bl -hang -width 4n .It Nm volume .Ar name .Op options .Pp Define a volume with name .Ar name . .Pp Options are: .Pp .Bl -hang -width 18n .It Nm plex Ar plexname Add the specified plex to the volume. If .Ar plexname is specified as .Ar * , .Nm will look for the definition of the plex as the next possible entry in the configuration file after the definition of the volume. .It Nm readpol Ar policy Define a .Ar read policy for the volume. .Ar policy may be either .Nm round or .Nm prefer Ar plexname . .Nm satisfies a read request from only one of the plexes. A .Ar round read policy specifies that each read should be performed from a different plex in \fIround-robin\fR\| fashion. A .Ar prefer read policy reads from the specified plex every time. .It Nm setupstate .Pp When creating a multi-plex volume, assume that the contents of all the plexes are consistent. This is normally not the case, and correctly you should use the .Nm init command to first bring them to a consistent state. In the case of striped and concatenated plexes, however, it does not normally cause problems to leave them inconsistent: when using a volume for a file system or a swap partition, the previous contents of the disks are not of interest, so they may be ignored. If you want to take this risk, use this keyword. It will only apply to the plexes defined immediately after the volume in the configuration file. If you add plexes to a volume at a later time, you must integrate them. .Pp Note that you \fImust\fP\| use the .Nm init command with RAID-5 plexes: otherwise extreme data corruption will result if one subdisk fails. .fi .El .It Nm plex Op options .Pp Define a plex. Unlike a volume, a plex does not need a name. The options may be: .Pp .Bl -hang -width 18n .It Nm name Ar plexname Specify the name of the plex. Note that you must use the keyword .Ar name when naming a plex or subdisk. .sp .It Nm org Ar organization Op stripesize .Pp Specify the organization of the plex. .Ar organization can be one of .Ar concat , .Ar striped or .Ar raid5 . For .Ar striped and .Ar raid5 plexes, the parameter .Ar stripesize must be specified, while for .Ar concat it must be omitted. For type .Ar striped , it specifies the width of each stripe. For type .Ar raid5 , it specifies the size of a group. A group is a portion of a plex which stores the parity bits all in the same subdisk. It must be a factor of the plex size (in other words, the result of dividing the plex size by the stripe size must be an integer), and it must be a multiple of a disk sector (512 bytes). .sp For optimum performance, stripes should be at least 128 kB in size: anything smaller will result in a significant increase in I/O activity due to mapping of individual requests over multiple disks. The performance improvement due to the increased number of concurrent transfers caused by this mapping will not make up for the performance drop due to the increase in latency. A good guideline for stripe size is between 256 kB and 512 kB. .Pp A striped plex must have at least two subdisks (otherwise it is a concatenated plex), and each must be the same size. A RAID-5 plex must have at least three subdisks, and each must be the same size. In practice, a RAID-5 plex should have at least 5 subdisks. .Pp .It Nm volume Ar volname Add the plex to the specified volume. If no .Nm volume keyword is specified, the plex will be added to the last volume mentioned in the configuration file. .sp .It Nm sd Ar sdname Ar offset Add the specified subdisk to the plex at offset .Ar offset . .br .fi .El .It Nm subdisk Op options .Pp Define a subdisk. Options may be: .Pp .Bl -hang -width 18n .nf .sp .It Nm name Ar name Specify the name of a subdisk. It is not necessary to specify a name for a subdisk\(emsee OBJECT NAMING above. Note that you must specify the keyword .Ar name if you wish to name a subdisk. .sp .It Nm plexoffset Ar offset Specify the starting offset of the subdisk in the plex. If not specified, .Nm allocates the space immediately after the previous subdisk, if any, or otherwise at the beginning of the plex. .sp .It Nm driveoffset Ar offset Specify the starting offset of the subdisk in the drive. If not specified, .Nm allocates the first contiguous .Ar length bytes of free space on the drive. .sp .It Nm length Ar length Specify the length of the subdisk. This keyword must be specified. There is no default, but the value 0 may be specified to mean .if t ``use the largest available contiguous free area on the drive''. .if n "use the largest available contiguous free area on the drive". If the drive is empty, this means that the entire drive will be used for the subdisk. .Nm length may be shortened to .Nm len . .sp .It Nm plex Ar plex Specify the plex to which the subdisk belongs. By default, the subdisk belongs to the last plex specified. .sp .It Nm drive Ar drive Specify the drive on which the subdisk resides. By default, the subdisk resides on the last drive specified. .br .fi .El .It Nm drive Ar name Op options .Pp Define a drive. The option must be: .Pp .Bl -hang -width 18n .It Nm device Ar devicename Specify the device on which the drive resides. .El .El .Sh EXAMPLE CONFIGURATION FILE .Bd -literal # Sample vinum configuration file # # Our drives drive drive1 device /dev/da1h drive drive2 device /dev/da2h drive drive3 device /dev/da3h drive drive4 device /dev/da4h drive drive5 device /dev/da5h drive drive6 device /dev/da6h # A volume with one striped plex volume tinyvol plex org striped 512b sd length 64m drive drive2 sd length 64m drive drive4 volume stripe plex org striped 512b sd length 512m drive drive2 sd length 512m drive drive4 # Two plexes volume concat plex org concat sd length 100m drive drive2 sd length 50m drive drive4 plex org concat sd length 150m drive drive4 # A volume with one striped plex and one concatenated plex volume strcon plex org striped 512b sd length 100m drive drive2 sd length 100m drive drive4 plex org concat sd length 150m drive drive2 sd length 50m drive drive4 # a volume with a RAID-5 and a striped plex # note that the RAID-5 volume is longer by # the length of one subdisk volume vol5 plex org striped 64k sd length 1000m drive drive2 sd length 1000m drive drive4 plex org raid5 32k sd length 500m drive drive1 sd length 500m drive drive2 sd length 500m drive drive3 sd length 500m drive drive4 sd length 500m drive drive5 .Ed .Ss DRIVE LAYOUT CONSIDERATIONS .Nm drives are currently BSD disk partitions. They must be of type .Ar vinum in order to avoid overwriting file systems. For compatibility reasons, .Nm currently accepts partitions of type .Ar unused , but the next release will not allow this kind of partition. .Nm prints a warning message when reading a configuration from a partition of type .Ar unused . Use .Nm disklabel .Ar -e to edit a partition type definition. The following display shows a typical partition layout as shown by .Nm disklabel: .Bd -literal 8 partitions: # size offset fstype [fsize bsize bps/cpg] a: 81920 344064 4.2BSD 0 0 0 # (Cyl. 240*- 297*) b: 262144 81920 swap # (Cyl. 57*- 240*) c: 4226725 0 unused 0 0 # (Cyl. 0 - 2955*) e: 81920 0 4.2BSD 0 0 0 # (Cyl. 0 - 57*) f: 1900000 425984 4.2BSD 0 0 0 # (Cyl. 297*- 1626*) g: 1900741 2325984 vinum 0 0 0 # (Cyl. 1626*- 2955*) .Ed .sp In this example, partition .Nm g may be used as a .Nm partition. Partitions .Nm a , .Nm e and .Nm f may be used as .Nm UFS file systems or .Nm ccd partitions. Partition .Nm b is a swap partition, and partition .Nm c represents the whole disk and should not be used for any other purpose. .Pp .Nm uses the first 265 sectors on each partition for configuration information, so the maximum size of a subdisk is 265 sectors smaller than the drive. .Sh HOW TO SET UP VINUM This section gives practical advice about how to implement a .Nm system. .Ss Where to put the data The first choice you need to make is where to put the data. You need dedicated disk partitions for .Nm vinum . See the example under DRIVE LAYOUT CONSIDERATIONS above. Choose partition type .Nm unless your version of .Xr disklabel 8 does not understand this partition type, in which case you will need to use partition type .Nm unused until you update your version of .Xr disklabel 8 . Use the compatibility partition (for example, .Pa /dev/da0g ) rather than the true partition name (such as .Pa /dev/da0s1g ). .Nm currently uses the compatibility partition only for the .Nm start command, so this way you can avoid problems. .Ss Designing volumes The way you set up .Nm volumes depends on your intentions. There are a number of possibilities: .Bl -enum .It You may want to join up a number of small disks to make a reasonable sized file system. For example, if you had five small drives and wanted to use all the space for a single volume, you might write a configuration file like: .Bd -literal -offset 4n drive d1 device /dev/da2e drive d2 device /dev/da3e drive d3 device /dev/da4e drive d4 device /dev/da5e drive d5 device /dev/da6e volume bigger plex org concat sd length 0 drive d1 sd length 0 drive d2 sd length 0 drive d3 sd length 0 drive d4 sd length 0 drive d5 .Ed .Pp In this case, you specify the length of the subdisks as 0, which means .if t ``use the largest area of free space that you can find on the drive''. .if n "use the largest area of free space that you can find on the drive". If the subdisk is the only subdisk on the drive, it will use all available space. .It You want to set up .Nm to obtain additional resilience against disk failures. You have the choice of RAID-1, also called .if t ``mirroring'', or RAID-5, also called ``parity''. .if n "mirroring", or RAID-5, also called "parity". .Pp To set up mirroring, create multiple plexes in a volume. For example, to create a mirrored volume of 2 GB, you might create the following configuration file: .Bd -literal -offset 4n drive d1 device /dev/da2e drive d2 device /dev/da3e volume mirror plex org concat sd length 2g drive d1 plex org concat sd length 2g drive d2 .Ed .Pp When creating mirrored drives, it is important to ensure that the data from each plex is on a different physical disk so that .Nm can access the complete address space of the volume even if a drive fails. Note that each plex requires as much data as the complete volume: in this example, the volume has a size of 2 GB, but each plex (and each subdisk) requires 2 GB, so the total disk storage requirement is 4 GB. .Pp To set up RAID-5, create a single plex of type .Ar raid5 . For example, to create an equivalent resilient volume of 2 GB, you might use the following configuration file: .Bd -literal -offset 4n drive d1 device /dev/da2e drive d2 device /dev/da3e drive d3 device /dev/da4e drive d4 device /dev/da5e drive d5 device /dev/da6e volume raid plex org raid5 512k sd length 512m drive d1 sd length 512m drive d2 sd length 512m drive d3 sd length 512m drive d4 sd length 512m drive d5 .Ed .Pp RAID-5 plexes require at least three subdisks, one of which is used for storing parity information and is lost for data storage. The more disks you use, the greater the proportion of the disk storage can be used for data storage. In this example, the total storage usage is 2.5 GB, compared to 4 GB for a mirrored configuration. If you were to use the minimum of only three disks, you would require 3 GB to store the information, for example: .Bd -literal -offset 4n drive d1 device /dev/da2e drive d2 device /dev/da3e drive d3 device /dev/da4e volume raid plex org raid5 512k sd length 1g drive d1 sd length 1g drive d2 sd length 1g drive d3 .Ed .Pp As with creating mirrored drives, it is important to ensure that the data from each subdisk is on a different physical disk so that .Nm can access the complete address space of the volume even if a drive fails. .It You want to set up .Nm to allow more concurrent access to a file system. In many cases, access to a file system is limited by the speed of the disk. By spreading the volume across multiple disks, you can increase the throughput in multi-access environments. This technique shows little or no performance improvement in single-access environments. .Nm uses a technique called .if t ``striping'', .if n "striping", or sometimes RAID-0, to increase this concurrency of access. The name RAID-0 is misleading: striping does not provide any redundancy or additional reliability. In fact, it decreases the reliability, since the failure of a single disk will render the volume useless, and the more disks you have, the more likely it is that one of them will fail. .Pp To implement striping, use a .Ar striped plex: .Bd -literal -offset 4n drive d1 device /dev/da2e drive d2 device /dev/da3e drive d3 device /dev/da4e drive d4 device /dev/da5e volume raid plex org striped 512k sd length 512m drive d1 sd length 512m drive d2 sd length 512m drive d3 sd length 512m drive d4 .Ed .Pp A striped plex must have at least two subdisks, but the increase in performance is greater if you have a larger number of disks. .It You may want to have the best of both worlds and have both resilience and performance. This is sometimes called RAID-10 (a combination of RAID-1 and RAID-0), though again this name is misleading. With .Nm you can do this with the following configuration file: .Bd -literal -offset 4n drive d1 device /dev/da2e drive d2 device /dev/da3e drive d3 device /dev/da4e drive d4 device /dev/da5e volume raid plex org striped 512k sd length 512m drive d1 sd length 512m drive d2 sd length 512m drive d3 sd length 512m drive d4 plex org striped 512k sd length 512m drive d4 sd length 512m drive d3 sd length 512m drive d2 sd length 512m drive d1 .Ed .Pp Here the plexes are striped, increasing performance, and there are two of them, increasing reliablity. Note that this example shows the subdisks of the second plex in reverse order from the first plex. This is for performance reasons and will be discussed below. .El .Ss Creating the volumes Once you have created your configuration files, start .Nm and create the volumes. In this example, the configuration is in the file .Pa configfile : .Bd -literal # vinum create -v configfile 1: drive d1 device /dev/da2e 2: drive d2 device /dev/da3e 3: volume mirror 4: plex org concat 5: sd length 2g drive d1 6: plex org concat 7: sd length 2g drive d2 Configuration summary Drives: 2 (4 configured) Volumes: 1 (4 configured) Plexes: 2 (8 configured) Subdisks: 2 (16 configured) Drive d1: Device /dev/da2e Created on vinum.lemis.com at Tue Mar 23 12:30:31 1999 Config last updated Tue Mar 23 14:30:32 1999 Size: 60105216000 bytes (57320 MB) Used: 2147619328 bytes (2048 MB) Available: 57957596672 bytes (55272 MB) State: up Last error: none Drive d2: Device /dev/da3e Created on vinum.lemis.com at Tue Mar 23 12:30:32 1999 Config last updated Tue Mar 23 14:30:33 1999 Size: 60105216000 bytes (57320 MB) Used: 2147619328 bytes (2048 MB) Available: 57957596672 bytes (55272 MB) State: up Last error: none Volume mirror: Size: 2147483648 bytes (2048 MB) State: up Flags: 2 plexes Read policy: round robin Plex mirror.p0: Size: 2147483648 bytes (2048 MB) Subdisks: 1 State: up Organization: concat Part of volume mirror Plex mirror.p1: Size: 2147483648 bytes (2048 MB) Subdisks: 1 State: up Organization: concat Part of volume mirror Subdisk mirror.p0.s0: Size: 2147483648 bytes (2048 MB) State: up Plex mirror.p0 at offset 0 Subdisk mirror.p1.s0: Size: 2147483648 bytes (2048 MB) State: up Plex mirror.p1 at offset 0 .Ed .Pp The .Fl v flag tells .Nm to list the file as it configures. Subsequently it lists the current configuration in the same format as the .Nm list command. .Ss Creating more volumes Once you have created the .Nm volumes, .Nm keeps track of them in its internal configuration files. You do not need to create them again. In particular, if you run the .Nm create command again, you will create additional objects: .Bd -literal .if t .ps -2 # vinum create sampleconfig Configuration summary Drives: 2 (4 configured) Volumes: 1 (4 configured) Plexes: 4 (8 configured) Subdisks: 4 (16 configured) D d1 State: up Device /dev/da2e Avail: 53224/57320 MB (92%) D d2 State: up Device /dev/da3e Avail: 53224/57320 MB (92%) V mirror State: up Plexes: 4 Size: 2048 MB P mirror.p0 C State: up Subdisks: 1 Size: 2048 MB P mirror.p1 C State: up Subdisks: 1 Size: 2048 MB P mirror.p2 C State: up Subdisks: 1 Size: 2048 MB P mirror.p3 C State: up Subdisks: 1 Size: 2048 MB S mirror.p0.s0 State: up PO: 0 B Size: 2048 MB S mirror.p1.s0 State: up PO: 0 B Size: 2048 MB S mirror.p2.s0 State: up PO: 0 B Size: 2048 MB S mirror.p3.s0 State: up PO: 0 B Size: 2048 MB .if t .ps .Ed .Pp As this example (this time with the .Fl f flag) shows, re-running the .Nm create has created four new plexes, each with a new subdisk. If you want to add other volumes, create new configuration files for them. They do not need to reference the drives that .Nm already knows about. For example, to create a volume .Pa raid on the four drives .Pa /dev/da1e , .Pa /dev/da2e , .Pa /dev/da3e and .Pa /dev/da4e , you only need to mention the other two: .Bd -literal drive d3 device /dev/da1e drive d4 device /dev/da4e volume raid plex org raid5 512k sd size 2g drive d1 sd size 2g drive d2 sd size 2g drive d3 sd size 2g drive d4 .Ed .Ss Performance considerations A number of misconceptions exist about how to set up a RAID array for best performance. In particular, most systems use far too small a stripe size. The following discussion applies to all RAID systems, not just to .Nm vinum . .Pp The FreeBSD block I/O system issues requests of between .5kB and 60 kB; a typical mix is somewhere round 8 kB. You can't stop any striping system from breaking a request into two physical requests, and if you do it wrong it can be broken into several. This will result in a significant drop in performance: the decrease in transfer time per disk is offset by the order of magnitude greater increase in latency. .Pp With modern disk sizes and the FreeBSD block I/O system, you can expect to have a reasonably small number of fragmented requests with a stripe size between 256 kB and 512 kB; with correct RAID implementations there is no obvious reason not to increase the size to 2 or 4 MB on a large disk. .Pp The easiest way to consider the impact of any transfer in a multi-access system is to look at it from the point of view of the potential bottleneck, the disk subsystem: how much total disk time does the transfer use? Since just about everything is cached, the time relationship between the request and its completion is not so important: the important parameter is the total time that the request keeps the disks active, the time when the disks are not available to perform other transfers. As a result, it doesn't really matter if the transfers are happening at the same time or different times. In practical terms, the time we're looking at is the sum of the total latency (positioning time and rotational latency, or the time it takes for the data to arrive under the disk heads) and the total transfer time. For a given transfer to disks of the same speed, the transfer time depends only on the total size of the transfer. .Pp Consider a typical news article or web page of 24 kB, which will probably be read in a single I/O. Take disks with a transfer rate of 6 MB/s and an average positioning time of 8 ms, and a file system with 4 kB blocks. Since it's 24 kB, we don't have to worry about fragments, so the file will start on a 4 kB boundary. The number of transfers required depends on where the block starts: it's (S + F - 1) / S, where S is the stripe size in file system blocks, and F is the file size in file system blocks. .Pp .Bl -enum .It Stripe size of 4 kB. You'll have 6 transfers. Total subsystem load: 48 ms latency, 2 ms transfer, 50 ms total. .It Stripe size of 8 kB. On average, you'll have 3.5 transfers. Total subsystem load: 28 ms latency, 2 ms transfer, 30 ms total. .It Stripe size of 16 kB. On average, you'll have 2.25 transfers. Total subsystem load: 18 ms latency, 2 ms transfer, 20 ms total. .It Stripe size of 256 kB. On average, you'll have 1.08 transfers. Total subsystem load: 8.6 ms latency, 2 ms transfer, 10.6 ms total. .It Stripe size of 4 MB. On average, you'll have 1.0009 transfers. Total subsystem load: 8.01 ms latency, 2 ms transfer, 10.01 ms total. .El .Pp It appears that some hardware RAID systems have problems with large stripes: they appear to always transfer a complete stripe to or from disk, so that a large stripe size will have an adverse effect on performance. .Nm does not suffer from this problem: it optimizes all disk transfers and does not transfer unneeded data. .Pp Note that no well-known benchmark program tests true multi-access conditions (more than 100 concurrent users), so it is difficult to demonstrate the validity of these statements. .Pp Given these considerations, the following factors affect the performance of a .Nm volume: .Bl -bullet .It Striping improves performance for multiple access only, since it increases the chance of individual requests being on different drives. .It Concatenating UFS file systems across multiple drives can also improve performance for multiple file access, since UFS divides a file system into cylinder groups and attempts to keep files in a single cylinder group. In general, it is not as effective as striping. .It Mirroring can improve multi-access performance for reads, since by default .Nm issues consecutive reads to consecutive plexes. .It Mirroring decreases performance for all writes, whether multi-access or single access, since the data must be written to both plexes. This explains the subdisk layout in the example of a mirroring configuration above: if the corresponding subdisk in each plex is on a different physical disk, the write commands can be issued in parallel, whereas if they are on the same physical disk, they will be performed sequentially. .It RAID-5 reads have essentially the same considerations as striped reads, unless the striped plex is part of a mirrored volume, in which case the performance of the mirrored volume will be better. .It RAID-5 writes are approximately 25% of the speed of striped writes: to perform the write, .Nm must first read the data block and the corresponding parity block, perform some calculations and write back the parity block and the data block, four times as many transfers as for writing a striped plex. On the other hand, this is offset by the cost of mirroring, so writes to a volume with a single RAID-5 plex are approximately half the speed of writes to a correctly configured volume with two striped plexes. .It When the .Nm configuration changes (for example, adding or removing objects, or the change of state of one of the objects), .Nm writes up to 128 kB of updated configuration to each drive. The larger the number of drives, the longer this takes. .El .Ss Creating file systems on Vinum volumes You do not need to run .Nm disklabel before creating a file system on a .Nm volume. Just run .Nm newfs against the raw device. Use the .Fl v option to state that the device is not divided into partitions. For example, to create a file system on volume .Pa mirror , enter the following command: .Bd -literal -offset 4n # newfs -v /dev/vinum/rmirror .Ed .Pp Note the name .Pa rmirror , indicating the raw device. .Sh Other considerations A number of other considerations apply to .Nm configuration: .Bl -bullet .It There is no advantage in creating multiple drives on a single disk. Each drive uses 131.5 kB of data for label and configuration information, and performance will suffer when the configuration changes. Use appropriately sized subdisks instead. .It It is possible to increase the size of a concatenated .Nm plex, but currently the size of striped and RAID-5 plexes cannot be increased. Currently the size of an existing UFS file system also cannot be increased, but it is planned to make both plexes and file systems extensible. .El .Sh GOTCHAS The following points are not bugs, and they have good reasons for existing, but they have shown to cause confusion. Each is discussed in the appropriate section above. .Bl -enum .It .Nm will not create a device on UFS partitions. Instead, it will return an error message .if t ``wrong partition type''. .if n "wrong partition type". The partition type should be .Ar vinum , though currently partitions of type .Ar unused are also accepted. .It When you create a volume with multiple plexes, .Nm does not automatically initialize the plexes. This means that the contents are not known, but they are certainly not consistent. As a result, by default .Nm sets the state of all newly-created plexes except the first to .Ar stale . In order to synchronize them with the first plex, you must .Nm start their subdisks, which causes .Nm to copy the data from a plex which is in the .Ar up state. Depending on the size of the subdisks involved, this can take a long time. .Pp In practice, people aren't too interested in what was in the plex when it was created, and other volume managers cheat by setting them .Ar up anyway. .Nm provides two ways to ensure that newly created plexes are .Ar up : .Bl -bullet .It Create the plexes and then synchronize them with .Nm vinum start . .It Create the volume (not the plex) with the keyword .Ar setupstate , which tells .Nm to ignore any possible inconsistency and set the plexes to be .Ar up . .El .It Some of the commands currently supported by .Nm are not really needed. For reasons which I don't understand, however, I find that users frequently try the .Nm label and .Nm resetconfig commands, though especially .Nm resetconfig outputs all sort of dire warnings. Don't use these commands unless you have a good reason to do so. .It Some state transitions are not very intuitive. In fact, it's not clear whether this is a bug or a feature. If you find that you can't start an object in some strange state, such as a .Ar reborn subdisk, try first to get it into .Ar stopped state, with the .Nm stop or .Nm stop Ar -f commands. If that works, you should then be able to start it. If you find that this is the only way to get out of a position where easier methods fail, please report the situation. .It If you build the kernel module with the .Ar -DVINUMDEBUG option, you must also build .Nm vinum(8) with the .Ar -DVINUMDEBUG option, since the size of some data objects used by both components depends on this option. If you don't do so, commands will fail with the message .Ar Invalid argument , and a console message will be logged such as .Pp .Bd -literal vinumioctl: invalid ioctl from process 247 (vinum): c0e44642 .Ed .Pp This error may also occur if you use old versions of kld or userland program. .El .\"XXX.Sh BUGS .Sh FILES .Ar /dev/vinum - directory with device nodes for .Nm objects. .br .Ar /dev/vinum/control - control device for .Nm vinum .br .Ar /dev/vinum/plex - directory containing device nodes for .Nm plexes. .br .Ar /dev/vinum/sd - directory containing device nodes for .Nm subdisks. .Sh SEE ALSO .Xr vinum 4 , .Xr disklabel 8 , .Xr newfs 8 , .Pa http://www.lemis.com/vinum.html , .Pa http://www.lemis.com/vinum-debugging.html . .Sh AUTHOR Greg Lehey .Pa . .Sh HISTORY The .Nm command first appeared in FreeBSD 3.0.