.\"	$OpenBSD: softraid.4,v 1.3 2007/03/26 00:31:50 tedu Exp $
.\"
.\" Copyright (c) 2007 Todd T. Fries <todd@OpenBSD.org>
.\"
.\" Permission to use, copy, modify, and distribute this software for any
.\" purpose with or without fee is hereby granted, provided that the above
.\" copyright notice and this permission notice appear in all copies.
.\"
.\" THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
.\" WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
.\" MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
.\" ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
.\" WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
.\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
.\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
.\"
.Dd March 19, 2007
.Dt SOFTRAID 4
.Os
.Sh NAME
.Nm softraid
.Nd Software RAID
.Sh SYNOPSIS
.Cd "softraid0 at root"
.Cd "scsibus*  at softraid?"
.Sh DESCRIPTION
The
.Nm
driver provides RAID 1 capabilities to
.Ox .
.Pp
It provides a single RAID level:
.Bl -tag -width indent -offset indent
.\" .It RAID 0
.\" provides simple data striping across the components.
.It RAID 1
provides mirroring.
.\" .It RAID 5
.\" provides data striping across the components, with parity
.\" distributed across all the components.
.El
.Pp
See
.Xr bioctl 8
for more information on configuration of RAID sets.
.Pp
The first step to using the
.Nm
driver is to ensure that it is suitably configured in the kernel.
This is done by adding the following lines
to the kernel configuration file:
.Bd -literal -offset indent
softraid0       at root         # Software RAID
scsibus*        at softraid?
.Ed
.Pp
All component partitions must be of type
.Dv RAID .
Some platforms, such as SUN, are not capable of using the
.Dv RAID
partition type.
The
.Dv 4.2BSD
partition type should be used on such platforms.
.Sh SEE ALSO
.Xr sd 4 ,
.Xr wd 4 ,
.Xr bioctl 8 ,
.Xr config 8 ,
.Xr fsck 8 ,
.Xr MAKEDEV 8 ,
.Xr mount 8 ,
.Xr newfs 8
.Sh HISTORY
The
.Nm
driver in
.Ox
is an original work by Marco Peereboom.
It first appeared in
.Ox 4.2 .
.Sh CAVEATS
RAID level 1 can protect against some
data loss due to component failure.
However the loss of any component of a RAID 0 system
will result in the entire filesystems on that RAID device
being lost.
RAID is
.Em not
a substitute for good backup practices.
.Sh BUGS
The driver is currently unable to handle drive failures.