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Update for recent addition of component labels and hot-adding spares.

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oster 1999-03-02 03:14:43 +00:00
parent 53d349a107
commit d17a319fc8
1 changed files with 29 additions and 4 deletions
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33
share/man/man4/raid.4
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@ -1,4 +1,4 @@
.\" $NetBSD: raid.4,v 1.3 1999/02/04 14:50:31 oster Exp $
.\" $NetBSD: raid.4,v 1.4 1999/03/02 03:14:43 oster Exp $
.\"
.\" Copyright (c) 1998 The NetBSD Foundation, Inc.
.\" All rights reserved.
@ -107,16 +107,41 @@ reconstructed from the data and parity present on the other
components. This results in much slower data accesses, but
does mean that a failure need not bring the system to a complete halt.
.Pp
The RAID driver supports and enforces the use of
.Sq component labels .
A
.Sq component label
contains important information about the component, including a
user-specified serial number, the row and column of that component in the RAID
set, and whether the data (and parity) on the component is
.Sq clean .
If the driver determines that the labels are very inconsistent with
respect to each other (e.g. two or more serial numbers do not match)
or that the component label is not consistent with it's assigned place
in the set (e.g. the component label claims the component should be
the 3rd one a 6-disk set, but the RAID set has it as the 3rd component
in a 5-disk set) then the device will fail to configure. If the
driver determines that exactly one component label seems to be
incorrect, and the RAID set is being configured as a set that supports
a single failure, then the RAID set will be allowed to configure, but
the incorrectly labeled component will be marked as
.Sq failed ,
and the RAID set will begin operation in degraded mode.
If all of the components are consistent among themselves, the RAID set
will configure normally.
.Pp
The driver supports
.Sq hot spares ,
disks which are on-line, but are not
actively used in an existing filesystem. Should a disk fail, the
driver is capable of reconstructing the failed disk onto a hot spare.
driver is capable of reconstructing the failed disk onto a hot spare
or back onto a replacment drive.
If the components are hot swapable, the failed disk can then be
removed, a new disk put in it's place, and a copyback operation
performed. The copyback operation, as it's name indicates, will copy
the reconstructed data from the hot spare to the previously failed
(and now replaced) disk.
(and now replaced) disk. Hot spares can also be hot-added using
.Xr raidctl 8 .
.Pp
If a component cannot be detected when the RAID device is configured,
that component will be simply marked as 'failed'.
@ -129,7 +154,7 @@ is
For any of the RAID flavours which have parity data,
.Xr raidctl 8
must be used with the
.Fl r
.Fl i
option to re-write the data when either a) a new RAID device is
brought up for the first time or b) after an un-clean shutdown of a
RAID device. By performing this on-demand recomputation of all parity