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Diffstat (limited to 'share')
| -rw-r--r-- | share/man/man4/ccd.4 | 55 |
1 files changed, 28 insertions, 27 deletions
diff --git a/share/man/man4/ccd.4 b/share/man/man4/ccd.4 index becf8343396..bd3ca8d0e53 100644 --- a/share/man/man4/ccd.4 +++ b/share/man/man4/ccd.4 @@ -1,4 +1,4 @@ -.\" $OpenBSD: ccd.4,v 1.20 2005/02/01 22:02:53 jmc Exp $ +.\" $OpenBSD: ccd.4,v 1.21 2005/02/02 10:59:18 jmc Exp $ .\" $NetBSD: ccd.4,v 1.5 1995/10/09 06:09:09 thorpej Exp $ .\" .\" Copyright (c) 1994 Jason Downs. @@ -47,10 +47,6 @@ The driver provides the capability of combining one or more disks/partitions into one virtual disk. .Pp -This document assumes that you're familiar with how to generate kernels, -how to properly configure disks and pseudo-devices in a kernel -configuration file, and how to partition disks. -.Pp Note that the .Sq raw partitions of the disks @@ -58,32 +54,34 @@ partitions of the disks be combined. Each component partition should be offset at least one cylinder from the beginning of the component disk. -This avoids potential conflicts between the component disk's disklabel and the -.Nm ccd Ns 's -disklabel. +This avoids potential conflicts between the component disk's +.Xr disklabel 8 +and the concatenated disk's disklabel. The kernel wants to only allow component partitions of type .Dv FS_CCD , but due to disklabel restrictions on some architectures will also accept component partitions of .Dv FS_BSDFFS . .Pp -In order to compile in support for the ccd, you must add a line similar -to the following to your kernel configuration file: -.Bd -unfilled -offset indent +In order to compile in support for +.Nm , +make sure your kernel configuration file contains a line +similar to the following (GENERIC does by default): +.Bd -literal -offset indent pseudo-device ccd 4 # concatenated disk devices .Ed .Pp -The count argument is how many -.Nm ccd Ns 's -memory is allocated for at boot time. +The optional +.Ar count +argument specifies how many +concatenated disk devices are allocated for at boot time. In this example, no more than 4 -.Nm ccd Ns 's may be configured. .Pp A .Nm -may be either serially concatenated, interleaved or mirrored. -To serially concatenate partitions specify an interleave factor of 0. +may be either serially concatenated, interleaved, or mirrored. +To serially concatenate partitions, specify an interleave factor of 0. Mirroring configurations require an even number of components. .Pp If a @@ -92,9 +90,12 @@ is interleaved correctly, a .Dq striping effect is achieved, which can increase performance. Finding the optimum interleave factor is a hard problem. -Some things to think about are the number of disks in the ccd, +Some things to think about are the number of disks in the +.Nm , the typical read-ahead opportunities, the filesystem blocksize, and if -it's possible to use the optimized ccd I/O protocol. +it's possible to use the optimized +.Nm +I/O protocol. The optimized protocol allows smaller interleave factors for a comparably cheap price but requires that the factor be a multiple of the software page size @@ -120,16 +121,10 @@ Note that best performance is achieved if all component disks have the same geometry and size. Optimum striping cannot occur with different disk types. .Pp -There is a run-time utility that is used for configuring -.Nm ccd Ns 's . +There is a run-time utility that is used for configuring concatenated disks. See .Xr ccdconfig 8 for more information. -.Sh WARNINGS -If just one (or more) of the disks in a -.Nm -fails, the entire -file system will be lost. .Sh FILES .Bl -tag -width tenletters+five -compact .It Pa /dev/{,r}ccd* @@ -138,10 +133,16 @@ ccd device special files .Sh SEE ALSO .Xr MAKEDEV 8 , .Xr ccdconfig 8 , -.Xr config 8 , +.Xr disklabel 8 , .Xr fsck 8 , +.Xr growfs 8 , .Xr mount 8 , .Xr newfs 8 .Sh HISTORY The concatenated disk driver was originally written at the University of Utah. +.Sh CAVEATS +If just one (or more) of the disks in a +concatenated disk +fails, the entire +file system will be lost. |