Thu Jul 28 18:25:22 2011 UTC ()
Document the need for zeroing out the first 64 blocks of a replacement
component in a failed RAID set in order to avoid potentially configuring
RAId 1 sets with erroneous values taken from random extent data in the
replacement component partitions.


(buhrow)
diff -r1.61 -r1.62 src/sbin/raidctl/raidctl.8
cvs diff -r1.61 -r1.62 src/sbin/raidctl/raidctl.8 (expand / switch to unified diff)

--- src/sbin/raidctl/raidctl.8 2010/01/27 09:26:16 1.61
+++ src/sbin/raidctl/raidctl.8 2011/07/28 18:25:22 1.62
@@ -1,14 +1,14 @@ @@ -1,14 +1,14 @@
1.\" $NetBSD: raidctl.8,v 1.61 2010/01/27 09:26:16 wiz Exp $ 1.\" $NetBSD: raidctl.8,v 1.62 2011/07/28 18:25:22 buhrow Exp $
2.\" 2.\"
3.\" Copyright (c) 1998, 2002 The NetBSD Foundation, Inc. 3.\" Copyright (c) 1998, 2002 The NetBSD Foundation, Inc.
4.\" All rights reserved. 4.\" All rights reserved.
5.\" 5.\"
6.\" This code is derived from software contributed to The NetBSD Foundation 6.\" This code is derived from software contributed to The NetBSD Foundation
7.\" by Greg Oster 7.\" by Greg Oster
8.\" 8.\"
9.\" Redistribution and use in source and binary forms, with or without 9.\" Redistribution and use in source and binary forms, with or without
10.\" modification, are permitted provided that the following conditions 10.\" modification, are permitted provided that the following conditions
11.\" are met: 11.\" are met:
12.\" 1. Redistributions of source code must retain the above copyright 12.\" 1. Redistributions of source code must retain the above copyright
13.\" notice, this list of conditions and the following disclaimer. 13.\" notice, this list of conditions and the following disclaimer.
14.\" 2. Redistributions in binary form must reproduce the above copyright 14.\" 2. Redistributions in binary form must reproduce the above copyright
@@ -1587,15 +1587,27 @@ RAID is @@ -1587,15 +1587,27 @@ RAID is
1587.Em NOT 1587.Em NOT
1588a substitute for good backup practices. 1588a substitute for good backup practices.
1589.Pp 1589.Pp
1590Recomputation of parity 1590Recomputation of parity
1591.Em MUST 1591.Em MUST
1592be performed whenever there is a chance that it may have been compromised. 1592be performed whenever there is a chance that it may have been compromised.
1593This includes after system crashes, or before a RAID 1593This includes after system crashes, or before a RAID
1594device has been used for the first time. 1594device has been used for the first time.
1595Failure to keep parity correct will be catastrophic should a 1595Failure to keep parity correct will be catastrophic should a
1596component ever fail \(em it is better to use RAID 0 and get the 1596component ever fail \(em it is better to use RAID 0 and get the
1597additional space and speed, than it is to use parity, but 1597additional space and speed, than it is to use parity, but
1598not keep the parity correct. 1598not keep the parity correct.
1599At least with RAID 0 there is no perception of increased data security. 1599At least with RAID 0 there is no perception of increased data security.
 1600.Pp
 1601When replacing a failed component of a RAID set, it is a good
 1602idea to zero out the first 64 blocks of the new component to insure the
 1603RAIDframe driver doesn't erroneously detect a component label in the
 1604new component. This is particularly true on
 1605.Em
 1606RAID 1
 1607sets because there is at most one correct component label in a failed RAID
 16081 installation, and the RAIDframe driver picks the component label with the
 1609highest serial number and modification value as the authoritative source
 1610for the failed RAID set when choosing which component label to use to
 1611configure the RAID set.
1600.Sh BUGS 1612.Sh BUGS
1601Hot-spare removal is currently not available. 1613Hot-spare removal is currently not available.