MFC: rev. 1.2

- Convert to new SYNOPSIS layout
- New Sentence, new line
- Remove eol whitespace
This commit is contained in:
brueffer 2006-06-25 19:47:45 +00:00
parent 6affff8115
commit b9ee3676a6

View File

@ -32,7 +32,19 @@
.Nm geom_fox
.Nd "GEOM based basic disk multipathing"
.Sh SYNOPSIS
.Cd "kldload geom_fox"
To compile this driver into the kernel,
place the following line in your
kernel configuration file:
.Bd -ragged -offset indent
.Cd "options GEOM_FOX"
.Ed
.Pp
Alternatively, to load the driver as a
module at boot time, place the following line in
.Xr loader.conf 5 :
.Bd -literal -offset indent
geom_fox_load="YES"
.Ed
.Sh DESCRIPTION
The intent of the
.Nm
@ -41,25 +53,26 @@ access devices.
Basic in the above sentence should be read as:
.Nm
only provides path failover functionality, not load balancing over
the available paths etc.
Using suitable hardware like SCSI or FibreChannel disks it is
possible to have multiple (typically 2) host bus adapters access
the available paths etc.
Using suitable hardware like SCSI or FibreChannel disks it is
possible to have multiple (typically 2) host bus adapters access
the same physical disk drive.
.Pp
Without a multipathing driver the
.Fx
kernel would probe the disks multiple times, resulting in the creation of
multiple
multiple
.Pa /dev
entries for the same underlying physical device.
A unique label written in the GEOM label area allows
.Nm
to detect multiple paths. Using this information it creates a unique
.Nm
to detect multiple paths.
Using this information it creates a unique
.Pa da#.fox
device.
.Pp
The
.Nm
The
.Nm
device is subsequently used by the
.Fx
kernel to access the disks.
@ -68,8 +81,8 @@ Multiple physical access paths ensure that even in case of a path failure the
kernel can continue to access the data.
.Pp
The
.Nm
driver will disallow write operations to the underlying devices once the
.Nm
driver will disallow write operations to the underlying devices once the
fox device has been opened for writing.
.Sh EXAMPLES
.Pp
@ -97,7 +110,7 @@ echo "GEOM::FOX someid" | dd of=/dev/da2 conv=sync
For FibreChannel devices it is suggested to use the Node World Wide
Name (Node WWN) as this is guaranteed by the FibreChannel standard to
be worldwide unique.
The use of the Port WWN not recommended as each port of a given
The use of the Port WWN not recommended as each port of a given
device has a different WWN, thereby confusing things.
.Pp
The Node WWN can be obtained from a verbose boot as in for example
@ -108,7 +121,7 @@ isp1: Target 1 (Loop 0x1) Port ID 0xe8 (role Target) Arrived
.Ed
.Pp
This Node WWN would then be used like so:
.Bd -literal
.Bd -literal
echo "GEOM::FOX 20000004cfc8aca2" | dd of=/dev/da2 conv=sync
.Ed
.Pp
@ -121,7 +134,7 @@ Once the labelling has been performed and assuming the
module is loaded the kernel will inform you that it has found a new
.Nm
device with a message similar to
.Bd -literal
.Bd -literal
Creating new fox (da2)
fox da2.fox lock 0xfffffc0000fdba20
.Ed
@ -164,12 +177,12 @@ da2.fox N/A da2
.Xr GEOM 4 ,
.Xr geom 8
.Sh CAVEATS
The
.Nm
The
.Nm
driver depends on the underlying hardware drivers to do the right thing in case
of a path failure.
If for example a hardware driver continues to retry forever,
.Nm
.Nm
is not able to re-initiate the I/O to an alternative physical path.
.Pp
You have to be very sure to provide a unique label for each of the
@ -194,8 +207,8 @@ The examples provided are too FibreChannel-centric.
.Sh AUTHORS
.An -nosplit
The
.Nm
.Nm
driver was written by
.An "Poul-Henning Kamp" Aq phk@FreeBSD.org .
This manual page was written by
This manual page was written by
.An "Wilko Bulte" Aq wilko@FreeBSD.org .