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-rw-r--r--share/man/man4/ccd.455
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.