From: Helge Hafting <helgehaf@aitel.hist.no>
To: Mike Fedyk <mfedyk@matchmail.com>
Cc: linux-kernel@vger.kernel.org
Subject: Re: Thoughts on using fs/jbd from drivers/md
Date: Tue, 21 May 2002 11:03:33 +0200 [thread overview]
Message-ID: <3CEA0D65.DA25FB09@aitel.hist.no> (raw)
In-Reply-To: <15587.18828.934431.941516@notabene.cse.unsw.edu.au> <20020516161749.D2410@redhat.com> <20020517182942.GF627@matchmail.com> <20020517193410.W2693@redhat.com> <20020518013537.GH627@matchmail.com>
Mike Fedyk wrote:
>
> Doesn't degraded mode imply that there are not any parity
> disk(raid4)/stripe(raid5) updates?
>
Degraded mode means one of the (redundant) disks have
failed and isn't used. In raid-4 that might be
the parity disk - and then you get the no parity
case.
But it might be a data disk that failed instead,
the missing data will be calculated from
parity when needed, and of course parity is
modified upon write so information
can be stored even though some storage is missing.
Raid-5 spreads the parity over all the disks
for performance, so wether a missing disk
translates to a missing parity stripe or a missing
data stripe depends on the exact
block number.
Helge Hafting
next prev parent reply other threads:[~2002-05-21 9:04 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-05-16 5:54 Thoughts on using fs/jbd from drivers/md Neil Brown
2002-05-16 15:17 ` Stephen C. Tweedie
2002-05-17 18:29 ` Mike Fedyk
2002-05-17 18:34 ` Stephen C. Tweedie
2002-05-18 1:35 ` Mike Fedyk
2002-05-18 12:47 ` Stephen C. Tweedie
2002-05-21 9:03 ` Helge Hafting [this message]
2002-05-26 8:41 ` Daniel Phillips
2002-05-27 11:34 ` Stephen C. Tweedie
2002-05-27 11:50 Neil Brown
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