From: Petr Rockai <prockai@redhat.com>
To: Phillip Susi <psusi@cfl.rr.com>
Cc: LVM general discussion and development <linux-lvm@redhat.com>
Subject: Re: [linux-lvm] LVM mirror questions
Date: Thu, 07 Oct 2010 14:14:43 +0200 [thread overview]
Message-ID: <87fwwijj2k.fsf@twilight.int.mornfall.net.> (raw)
In-Reply-To: <4CACC6B0.2030603@cfl.rr.com> (Phillip Susi's message of "Wed, 6 Oct 2010 14:57:52 -0400")
Phillip Susi <psusi@cfl.rr.com> writes:
>> LVM has a generation counter as well. It's only updated on metadata
>> writes though, so it doesn't cost anything. (Log is not part of metadata
>> in this sense.) When you lose a leg (and use dmeventd), the metadata on
>> the remaining PVs is updated to say that. The leg is also yanked from
>> the mirror. You can add it as a fresh image (with full resync) if it
>> ever comes back.
>
> Why a full resync? With mdadm, it just keeps flagging the dirty chunks
> so it only has to copy those when the other disk returns.
Because it's really hard to guarantee anything when you experience a
failure. The safe route is to discard any data on the failed
drive. Certainly better than winding up with a subtly corrupt mirror.
As I said before, if you experience that a lot, you should be using
replication not mirroring.
Yours,
Petr.
prev parent reply other threads:[~2010-10-07 12:14 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-10-04 23:55 [linux-lvm] LVM mirror questions Jay
2010-10-05 8:02 ` Petr Rockai
2010-10-06 15:50 ` Jay
2010-10-06 16:37 ` Ray Morris
2010-10-06 17:23 ` Petr Rockai
2010-10-05 15:40 ` Phillip Susi
2010-10-06 15:26 ` Jay
2010-10-06 17:03 ` Stuart D. Gathman
2010-10-06 17:40 ` Petr Rockai
2010-10-06 18:57 ` Phillip Susi
2010-10-07 12:14 ` Petr Rockai [this message]
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