ccd.c and ccd.4 from NetBSD-current circa 12/25/95.

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+.\"	$NetBSD: ccd.4,v 1.5 1995/10/09 06:09:09 thorpej Exp $
+.\"
+.\" Copyright (c) 1994 Jason Downs.
+.\" Copyright (c) 1994, 1995 Jason R. Thorpe.
+.\" All rights reserved.
+.\"
+.\" Redistribution and use in source and binary forms, with or without
+.\" modification, are permitted provided that the following conditions
+.\" are met:
+.\" 1. Redistributions of source code must retain the above copyright
+.\"    notice, this list of conditions and the following disclaimer.
+.\" 2. Redistributions in binary form must reproduce the above copyright
+.\"    notice, this list of conditions and the following disclaimer in the
+.\"    documentation and/or other materials provided with the distribution.
+.\" 3. All advertising materials mentioning features or use of this software
+.\"    must display the following acknowledgement:
+.\"	This product includes software developed for the NetBSD Project
+.\"	by Jason Downs and Jason R. Thorpe.
+.\" 4. Neither the name of the author nor the names of its contributors
+.\"    may be used to endorse or promote products derived from this software
+.\"    without specific prior written permission.
+.\"
+.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+.\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+.\" BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+.\" LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+.\" AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+.\" OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+.\" SUCH DAMAGE.
+.\"
+.Dd August 9, 1995
+.Dt CCD 4
+.Os NetBSD
+.Sh NAME
+.Nm ccd
+.Nd Concatenated Disk Driver
+.Sh SYNOPSIS
+.Cd "pseudo-device ccd 4"
+.Sh DESCRIPTION
+The
+.Nm
+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
+.Pa should not
+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 compoent disk's disklabel and the
+.Nm ccd's
+disklabel.  The kernel will only allow component partitions of type 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
+pseudo-device	ccd	4	# concatenated disk devices
+.Ed
+.Pp
+The count argument is how many
+.Nm ccds
+memory is allocated for a boot time.  In this example, no more than 4
+.Nm ccds
+may be configured.
+.Pp
+A
+.Nm ccd
+may be either serially concatenated or interleaved.  If a
+.Nm ccd
+is interleaved correctly, a
+.Dq striping
+effect is achieved, which can increase performance.  The optimum interleave
+factor is typically the size of a track.  Since the interleave factor
+is expressed in units of DEV_BSIZE, one must account for sector sizes
+other than DEV_BSIZE in order to calculate the correct interleave.
+The kernel will not allow an interleave factor less than the size
+of the largest component sector divided by DEV_BSIZE.
+.Pp
+Note that best performance is achieved if all compent disks have the same
+geometery and size.  Optimum striping cannot occur with different
+disk types.
+.Pp
+There is a run-time utility that is used for configuring
+.Nm ccds .
+See
+.Xr ccdconfig 8
+for more information.
+.Sh WARNINGS
+If just one (or more) of the disks in a
+.Nm ccd
+fails, the entire
+file system will be lost.
+.Sh FILES
+/dev/{,r}ccd* - ccd device special files.
+.Pp
+.Sh HISTORY
+The concatenated disk driver was originally written at the University of
+Utah.
+.Sh SEE ALSO
+.Xr MAKEDEV 8 ,
+.Xr ccdconfig 8 ,
+.Xr config 8 ,
+.Xr config.old 8 ,
+.Xr fsck 8 ,
+.Xr mount 8 ,
+.Xr newfs 8 .