From: Paul Clements <paul.clements@steeleye.com>
To: Mike Snitzer <snitzer@gmail.com>
Cc: linux-raid@vger.kernel.org, neilb@suse.de
Subject: Re: [PATCH] md: new bitmap sysfs interface
Date: Thu, 27 Jul 2006 10:55:32 -0400 [thread overview]
Message-ID: <44C8D3E4.8040600@steeleye.com> (raw)
In-Reply-To: <170fa0d20607270728y176c3faega872bfa031342485@mail.gmail.com>
Mike Snitzer wrote:
> On 7/26/06, Paul Clements <paul.clements@steeleye.com> wrote:
>> Right. At the time of the failover, there were (probably) blocks that
>> were out of sync between the primary and secondary.
>
> OK, so now that I understand the need to merge the bitmaps... the
> various scenarios that create this (potential) inconsistency are still
> unclear to me when you consider the different flavors of raid1. Is
> this inconsistency only possible if using async (aka write-behind)
> raid1?
No. Even with a synchronous (normal) raid1, you will probably have
blocks that are out of sync when one disk (or server) fails. This is
true even of raid1's using internal disks. That's why you resync the
array after a failure (of the system or of one of the disks). That's
exactly what the bitmap is for -- to optimize that resync.
--
Paul
next prev parent reply other threads:[~2006-07-27 14:55 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-07-25 6:30 [PATCH] md: new bitmap sysfs interface Paul Clements
2006-07-25 17:41 ` dave rientjes
2006-07-26 21:30 ` Mike Snitzer
2006-07-27 2:27 ` Paul Clements
2006-07-27 3:36 ` Mike Snitzer
2006-07-27 14:07 ` Paul Clements
2006-07-27 14:28 ` Mike Snitzer
2006-07-27 14:55 ` Paul Clements [this message]
2006-08-03 1:42 ` Neil Brown
2006-08-03 1:53 ` Paul Clements
2006-08-03 7:24 ` David Greaves
2006-08-03 15:39 ` Mr. James W. Laferriere
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