diff --git a/sbin/newfs/newfs.8 b/sbin/newfs/newfs.8 index 4eba3c7fa1bd..7d2edc00d14d 100644 --- a/sbin/newfs/newfs.8 +++ b/sbin/newfs/newfs.8 @@ -30,7 +30,7 @@ .\" SUCH DAMAGE. .\" .\" @(#)newfs.8 8.6 (Berkeley) 5/3/95 -.\" $Id: newfs.8,v 1.19 1998/11/28 09:59:40 rnordier Exp $ +.\" $Id: newfs.8,v 1.20 1998/11/29 13:09:01 bde Exp $ .\" .Dd May 3, 1995 .Dt NEWFS 8 @@ -162,15 +162,21 @@ See .Xr tunefs 8 for more details on how to set this option. .It Fl b Ar block-size -The block size of the file system, in bytes. +The block size of the file system, in bytes. It must be a power of 2. The +default size is 8192 bytes, and the smallest allowable size is 4096 bytes. .It Fl c Ar #cylinders/group -The number of cylinders per cylinder group in a file system. -The default value is 16. +The number of cylinders per cylinder group in a file system. The default value +is 16. The maximum value is dependent on a number of other parameters, in +particular the block size. The best way to find the maximum value for a +specific file system is to attempt to specify a value which is far too large: +.Nm +will print out the maximum value. .It Fl d Ar rotdelay -Specify the expected time (in milliseconds) to service a transfer -completion interrupt and initiate a new transfer on the same disk. -The default is 0 milliseconds. -See +This parameter once specified the minimum time in milliseconds required to +initiate another disk transfer on the same cylinder. It was used in determining +the rotationally optimal layout for disk blocks within a file. Modern disks +with read/write-behind achieve higher performance with this feature disabled, so +this value should be left at the default value of 0 milliseconds. See .Xr tunefs 8 for more details on how to set this option. .ne 1i @@ -183,13 +189,19 @@ See .Xr tunefs 8 for more details on how to set this option. .It Fl f Ar frag-size -The fragment size of the file system in bytes. +The fragment size of the file system in bytes. It must be a power of two +ranging in value between +.Ar blocksize/8 +and +.Ar blocksize . The default is 1024 bytes. .It Fl i Ar number of bytes per inode Specify the density of inodes in the file system. The default is to create an inode for every (4 * frag-size) bytes of data space. If fewer inodes are desired, a larger number should be used; to create more inodes a smaller number should be given. +One inode is required for each distinct file, so this value effectively +specifies the average file size on the file system. .It Fl m Ar free space \&% The percentage of space reserved from normal users; the minimum free space threshold. @@ -203,9 +215,14 @@ See .Xr tunefs 8 for more details on how to set this option. .It Fl n Ar number of distinguished rotational positions -Determine how many rotational time slots there are in one revolution of -the disk. Defaults to 1, which essentially disables the rotational position -table. +UFS has the ability to keep track of the availability of blocks at different +rotational positions, so that it could lay out the data to be picked up with +minimum rotational latency. This parameter specifies the default number of +rotational positions to distinguish. +.Pp +Nowadays this value should be set to 1 (which essentially disables the +rotational position table) because modern drives with read-ahead and +write-behind do better without the rotational position table. .It Fl o Ar optimization\ preference .Pq ``space'' or ``time'' The file system can either be instructed to try to minimize the time spent @@ -218,7 +235,12 @@ See .Xr tunefs 8 for more details on how to set this option. .It Fl s Ar size -The size of the file system in sectors. +The size of the file system in sectors. This value defaults to the size of the +raw partition specified in +.Ar special +(in other words, +.Nm +will use the entire partition for the file system). .It Fl v Specify that the disk does not contain any partitions, and that .Nm @@ -246,6 +268,8 @@ Used to describe perturbations in the media format to compensate for a slow controller. Track skew is the offset of sector 0 on track N relative to sector 0 on track N-1 on the same cylinder. +This option is of historical importance only; modern controllers are always fast +enough to handle operations back-to-back. .It Fl l Ar hardware sector interleave Used to describe perturbations in the media format to compensate for a slow controller. @@ -254,14 +278,19 @@ specified as the denominator of the ratio: .Dl sectors read/sectors passed over Thus an interleave of 1/1 implies contiguous layout, while 1/2 implies logical sector 0 is separated by one sector from logical sector 1. +This option is of historical importance only; the physical sector layout of +modern disks is not visible from outside. .It Fl p Ar spare sectors per track Spare sectors (bad sector replacements) are physical sectors that occupy space at the end of each track. They are not counted as part of the sectors/track .Pq Fl u since they are not available to the file system for data allocation. +This option is of historical importance only. Modern disks perform their own +bad sector allocation. .It Fl r Ar revolutions/minute -The speed of the disk in revolutions per minute. +The speed of the disk in revolutions per minute. This value is no longer of +interest, since all the parameters which depend on it are usually disabled. .ne 1i .It Fl t Ar #tracks/cylinder The number of tracks/cylinder available for data allocation by the file @@ -284,6 +313,8 @@ They are deducted from the sectors/track .Pq Fl u of the last track of each cylinder since they are not available to the file system for data allocation. +This option is of historical importance only. Modern disks perform their own +bad sector allocation. .El .Pp The options to the