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Re: [Qemu-devel] [RFC PATCH 0/2] Sheepdog: distributed storage system fo
From: |
Kevin Wolf |
Subject: |
Re: [Qemu-devel] [RFC PATCH 0/2] Sheepdog: distributed storage system for QEMU |
Date: |
Fri, 14 May 2010 10:32:26 +0200 |
User-agent: |
Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.9) Gecko/20100330 Fedora/3.0.4-1.fc12 Thunderbird/3.0.4 |
Am 13.05.2010 16:03, schrieb MORITA Kazutaka:
> To support snapshot in a protocol, I'd like to call the hander of the
> protocol driver in the following functions in block.c:
>
> bdrv_snapshot_create
> bdrv_snapshot_goto
> bdrv_snapshot_delete
> bdrv_snapshot_list
> bdrv_save_vmstate
> bdrv_load_vmstate
>
> Is it okay?
Yes, I think this is the way to go.
> In the case both format and protocol drivers support snapshots, I
> think it is better to call the format driver handler. Because qcow2
> is well known as a snapshot support format, so when users use qcow2,
> they expect to get snapshot with qcow2.
I agree.
> There is another problem to make the sheepdog driver be a protocol;
> how to deal with protocol specific create_options?
>
> For example, sheepdog supports cloning images as a format driver:
>
> $ qemu-img create -f sheepdog dst -b sheepdog:src
>
> But if the sheepdog driver is a protocol, error will occur.
>
> $ qemu-img create sheepdog:dst -b sheepdog:src
> Unknown option 'backing_file'
> qemu-img: Backing file not supported for file format 'raw'
>
> It is because the raw format doesn't support a backing_file option.
> To support the protocol specific create_options, if the format driver
> cannot parse some of the arguments, the protocol driver need to parse
> them.
That's actually a good point. Yes, I think it makes a lot of sense to
allow parameters to be passed to the protocol driver.
Also, I've never tried to create an image over a protocol other than
file. As far as I know, raw is the only format for which it should work
right now (at least in theory). As we're going forward, I'm planning to
convert the other drivers, too.
Kevin
[Qemu-devel] [RFC PATCH v2 2/3] block: call the snapshot handlers of the protocol drivers, MORITA Kazutaka, 2010/05/14
[Qemu-devel] [RFC PATCH v2 1/3] close all the block drivers before the qemu process exits, MORITA Kazutaka, 2010/05/14
[Qemu-devel] [RFC PATCH v2 0/3] Sheepdog: distributed storage system for QEMU, MORITA Kazutaka, 2010/05/14