Re: [Qemu-devel] [RFC PATCH] replication agent module

From: Kevin Wolf <kwolf@redhat.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: "תומר בן אור" <tomer@zertodata.com>,
	"Ori Mamluk" <omamluk@zerto.com>, "עודד קדם" <oded@zerto.com>,
	dlaor@redhat.com, qemu-devel@nongnu.org
Subject: Re: [Qemu-devel] [RFC PATCH] replication agent module
Date: Tue, 07 Feb 2012 15:53:27 +0100	[thread overview]
Message-ID: <4F313AE7.3050104@redhat.com> (raw)
In-Reply-To: <4F3137DB.1040503@redhat.com>

Am 07.02.2012 15:40, schrieb Paolo Bonzini:
> On 02/07/2012 03:06 PM, Ori Mamluk wrote:
>> The main issue about it is that the Rephub also needs the other
>> direction - to read the protected volume. I get the feeling that with
>> live block copy and NBD there's probably something that might fit
>> this need, no?
> 
> Yes, with two NBD sockets you could do it.  But would you use both at 
> the same time?  I would have thought that either the rephub is streaming 
> from the protected volume, or QEMU is streaming to the rephub.
> 
> The current streaming code in QEMU only deals with the former. 
> Streaming to a remote server would not be supported.

Eventually we'll want to have it. We have been discussing about a mirror
block driver more than once. I think the same thing could be reused for
both replication and pre-copy live block migration.

You would probably have some flags that describe differences in the
detail (e.g. whether to wait for the mirrored write or not), but they
should be relatively small.

Kevin