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Date: Mon, 20 Feb 2012 15:32:39 +0100
From: Paolo Bonzini <pbonzini@redhat.com>
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Subject: Re: [Qemu-devel] [RFC] Replication agent design (was [RFC PATCH]
 replication agent module)
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To: Ori Mamluk <omamluk@zerto.com>
Cc: Kevin Wolf <kwolf@redhat.com>, =?UTF-8?B?16rXldee16gg15HXnyDXkNeV16g=?= <tomer@zertodata.com>, Stefan Hajnoczi <stefanha@gmail.com>, dlaor@redhat.com, qemu-devel@nongnu.org, =?UTF-8?B?16LXldeT15Mg16fXk9ed?= <oded@zerto.com>, Yair Kuszpet <yairk@zerto.com>

On 02/19/2012 02:40 PM, Ori Mamluk wrote:
> 
> I think it might be better to go back to my original less generic design.
> We can regard it as a 'plugin' for a specific application - in this
> case, replication.
> I can add a plugin interface in the generic block layer that allows
> building a proper storage stack.
> The plugin will have capabilities like a filter driver - getting hold of
> the request on its way down (from VM to storage) and on its way up (IO
> completion), allowing to block or stall both.

I and Stefan talked about this recently... we called it a BlockListener.
 It seems like a good idea, and probably copy-on-read should be
converted in due to time to a BlockListener, too.

Paolo