On 07/02/2012 14:40, Anthony Liguori wrote:
On 02/07/2012 06:30 AM, Ori Mamluk wrote:
In addition, I don't see that the listener thread holds any lock while
it reads the image. I guess that during that period the guest runs
and may
race w/ this new thread.
Yes - I mentioned that in the patch mail as one of the open issues. Can
you direct me to the lock I need? The function I call from a new thread
context is bdrv_aio_readv.
One thing that has me confused about this proposal. Why not just make
rehub be an iSCSI target provider and call it a day?
You've got a point there. This also goes with what Kevin wrote about
splitting the IOs with a block driver and not at the generic level.
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?
With a 'new' agent like I need this is relatively easily achieved by a
bidirectional protocol, but I agree a more generic protocol would be
more elegant, although it will probably require a socket per direction, no?
I Some smaller questions:
* Is there already a working iScsi initiator as a block driver (I hope
I'm using the right terminology) in Qemu, or do I need to write one?
* This driver would need to be added in run-time - to allow starting to
protect a running VM. Maybe via a monitor command. I guess that's OK, right?
* What can you say about NBD via iScsi - with respect to our
requirements- who is more mature in Qemu?
One more thing about the iScsi initiator - it will not be a standard
backing for a drive, because the 'production' drive (i.e. the original
image) is more important than the replicated one. This means that even
though we use iScsi, this is still a replication agent - not a generic
'additional' iscsi backing.
Regards,
Anthony Liguori
-----Original Message-----
From: Dor Laor [mailto:dl...@redhat.com]
Sent: Tuesday, February 07, 2012 2:25 PM
To: Anthony Liguori
Cc: Ori Mamluk; Kevin Wolf; qemu-devel@nongnu.org
Subject: Re: [Qemu-devel] [RFC PATCH] replication agent module
On 02/07/2012 02:12 PM, Anthony Liguori wrote:
Hi,
On 02/07/2012 04:29 AM, Ori Mamluk wrote:
Repagent is a new module that allows an external replication system
to replicate a volume of a Qemu VM.
This RFC patch adds the repagent client module to Qemu.
Please read http://wiki.qemu.org/Contribute/SubmitAPatch
In particular, use a tool like git-send-email and split this patch up
into more manageable chunks.
Is there an Open Source rehub available? As a project policy, adding
external APIs specifically for proprietary software is not something
we're willing to do.
Regards,
Anthony Liguori
In addition, I don't see that the listener thread holds any lock
while it
reads the image. I guess that during that period the guest runs and may
race w/ this new thread.
About image ID for the replication hub, you can use the VM's pid or VM's
uuid paired w/ the specific disk uuid
Thanks,
Dor
