From: Bart Van Assche <bart.vanassche@gmail.com>
To: Andi Kleen <andi@firstfloor.org>
Cc: LKML <linux-kernel@vger.kernel.org>
Subject: Re: dm-multipath and write request ordering
Date: Tue, 14 Apr 2009 10:17:58 +0200 [thread overview]
Message-ID: <e2e108260904140117t274815c6uebe5438ba2bf17b6@mail.gmail.com> (raw)
In-Reply-To: <878wm3903h.fsf@basil.nowhere.org>
On Tue, Apr 14, 2009 at 9:16 AM, Andi Kleen <andi@firstfloor.org> wrote:
> Bart Van Assche <bart.vanassche@gmail.com> writes:
>> - Is it correct that round-robin load balancing can only work
>> correctly in such a setup with proper support for write barriers in
>> the device mapper ?
>
> No opinion on that one.
What I'm worried about is that write requests that have been passed to
dm_mp could arrive in another order at the target because of the
variable transport time of protocols like TCP/IP. This could cause
newer data to be overwritten by older data. Separating those write
requests by a barrier won't help because dm_mp ignores barriers.
Bart.
next prev parent reply other threads:[~2009-04-14 8:18 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-04-13 11:22 Bart Van Assche
2009-04-14 7:16 ` Andi Kleen
2009-04-14 8:17 ` Bart Van Assche [this message]
2009-04-16 15:38 ` Vladislav Bolkhovitin
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