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Re: [Qemu-devel] Block job commands in QEMU 1.2 [v2, including support f
From: |
Paolo Bonzini |
Subject: |
Re: [Qemu-devel] Block job commands in QEMU 1.2 [v2, including support for replication] |
Date: |
Fri, 25 May 2012 10:48:53 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:12.0) Gecko/20120430 Thunderbird/12.0.1 |
Il 24/05/2012 18:57, Eric Blake ha scritto:
> On 05/24/2012 07:41 AM, Paolo Bonzini wrote:
>> changes from v1:
>> - added per-job iostatus
>> - added description of persistent dirty bitmap
>>
>> The same content is also at
>> http://wiki.qemu.org/Features/LiveBlockMigration/1.2
>>
>
>> * query-block-jobs: BlockJobInfo gets two new fields, paused and
>> io-status. The job-specific iostatus is completely separate from the
>> block device iostatus.
>
> Is it still true that for mirror jobs, whether we are mirroring is still
> determined by whether 'len'=='offset'?
Yes.
>> * block-job-complete: force completion of mirroring and switching of the
>> device to the target, not related to the rest of the proposal.
>> Synchronously opens backing files if needed, asynchronously completes
>> the job.
>
> Can this be made part of a 'transaction'? Likewise, can
> 'block-job-cancel' be made part of a 'transaction'?
Both of them are asynchronous so they would not create an atomic
snapshot. We could add it later, in the meanwhile you can wrap with
fsfreeze/fsthaw.
> But now that you are adding the possibility of mirroring reverting
> to copying, there is a race where I can probe and see that we are
> in mirroring, then issue a 'block-job-cancel' to affect a copy operation,
> but in the meantime things reverted, and the cancel ends up leaving me
> with an incomplete copy.
Hmm, that's right. But then this can only happen if you have an error
in the target. I can make block-job-cancel _not_ resume a paused job.
Would that satisfy your needs?
>> Persistent dirty bitmap
>> =======================
>>
>> A persistent dirty bitmap can be used by management for two reasons.
>> When mirroring is used for continuous replication of storage, to record
>> I/O operations that happened while the replication server is not
>> connected or unavailable. When mirroring is used for storage migration,
>> to check after a management crash whether the VM must be restarted with
>> the source or the destination.
>
> Is there a particular file format for the dirty bitmap? Is there a
> header, or is it just straight bitmap, where the size of the file is an
> exact function of size of the file that it maps?
I think it could be just a straight bitmap.
>> management can restart the virtual
>> machine with /mnt/dest/diskname.img. If it has even a single zero bit,
>
> s/zero/non-zero/
Doh, of course.
Paolo
- [Qemu-devel] Block job commands in QEMU 1.2 [v2, including support for replication], (continued)
- [Qemu-devel] Block job commands in QEMU 1.2 [v2, including support for replication], Paolo Bonzini, 2012/05/24
- Re: [Qemu-devel] Block job commands in QEMU 1.2 [v2, including support for replication], Ori Mamluk, 2012/05/24
- Re: [Qemu-devel] Block job commands in QEMU 1.2 [v2, including support for replication], Geert Jansen, 2012/05/29
- Re: [Qemu-devel] Block job commands in QEMU 1.2 [v2, including support for replication], Paolo Bonzini, 2012/05/29
- Re: [Qemu-devel] Block job commands in QEMU 1.2 [v2, including support for replication], Geert Jansen, 2012/05/30
- Re: [Qemu-devel] Block job commands in QEMU 1.2 [v2, including support for replication], Paolo Bonzini, 2012/05/30
Re: [Qemu-devel] Block job commands in QEMU 1.2 [v2, including support for replication], Eric Blake, 2012/05/24
Re: [Qemu-devel] Block job commands in QEMU 1.2 [v2, including support for replication], Stefan Hajnoczi, 2012/05/25
Re: [Qemu-devel] Block job commands in QEMU 1.2 [v2, including support for replication], Stefan Hajnoczi, 2012/05/25
- Re: [Qemu-devel] Block job commands in QEMU 1.2 [v2, including support for replication], Paolo Bonzini, 2012/05/25
- Re: [Qemu-devel] Block job commands in QEMU 1.2 [v2, including support for replication], Stefan Hajnoczi, 2012/05/25
- Re: [Qemu-devel] Block job commands in QEMU 1.2 [v2, including support for replication], Paolo Bonzini, 2012/05/25
- Re: [Qemu-devel] Block job commands in QEMU 1.2 [v2, including support for replication], ronnie sahlberg, 2012/05/31
Re: [Qemu-devel] Block job commands in QEMU 1.2 [v2, including support for replication], Luiz Capitulino, 2012/05/25