[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [Qemu-devel] [PATCH v4 0/7] Drop in_use from BlockDriverState and en
From: |
Stefan Hajnoczi |
Subject: |
Re: [Qemu-devel] [PATCH v4 0/7] Drop in_use from BlockDriverState and enable point-in-time snapshot exporting over NBD |
Date: |
Fri, 22 Nov 2013 17:58:34 +0100 |
User-agent: |
Mutt/1.5.21 (2010-09-15) |
On Fri, Nov 22, 2013 at 01:24:47PM +0800, Fam Zheng wrote:
> This series adds for point-in-time snapshot NBD exporting based on
> blockdev-backup (variant of drive-backup with existing device as target).
>
> We get a thin point-in-time snapshot by COW mechanism of drive-backup, and
> export it through built in NBD server. The steps are as below:
>
> 1. (SHELL) qemu-img create -f qcow2 BACKUP.qcow2 <source size here>
>
> (Alternatively we can use -o backing_file=RUNNING-VM.img to omit
> explicitly
> providing the size by ourselves, but it's risky because RUNNING-VM.qcow2
> is
> used r/w by guest. Whether or not setting backing file in the image file
> doesn't matter, as we are going to override the backing hd in the next
> step)
>
> 2. (QMP) blockdev-add backing=source-drive file.driver=file
> file.filename=BACKUP.qcow2 id=target0 if=none driver=qcow2
>
> (where ide0-hd0 is the running BlockDriverState name for
> RUNNING-VM.img. This patch implements "backing=" option to override
> backing_hd for added drive)
>
> 3. (QMP) blockdev-backup device=source-drive sync=none target=target0
>
> (this is the QMP command introduced by this series, which use a named
> device as target of drive-backup)
>
> 4. (QMP) nbd-server-add device=target0
>
> When image fleecing done:
>
> 1. (QMP) block-job-complete device=ide0-hd0
>
> 2. (HMP) drive_del target0
>
> 3. (SHELL) rm BACKUP.qcow2
Interesting implementation, it looks pretty good. I'll need to review
it a second time to track all the operation block/unblocks. It wasn't
immediately clear to me whether these patches will restrict something
that used to work.
Stefan
- Re: [Qemu-devel] [PATCH v4 4/7] block: Add checks of blocker in block operations, (continued)
- Re: [Qemu-devel] [PATCH v4 0/7] Drop in_use from BlockDriverState and enable point-in-time snapshot exporting over NBD,
Stefan Hajnoczi <=