[Sheepdog] Backup/Images

[Liu Yuan]

On 10/10/2011 11:39 AM, MORITA Kazutaka wrote:
> At Sun, 09 Oct 2011 14:27:41 +0800,
> Liu Yuan wrote:
>> On 10/09/2011 02:21 PM, Yibin Shen wrote:
>>>
>>> On Sun, Oct 9, 2011 at 1:33 PM, Liu Yuan<namei.unix at gmail.com
>>> <mailto:namei.unix at gmail.com>>  wrote:
>>>
>>>      On 10/09/2011 01:07 PM, MORITA Kazutaka wrote:
>>>
>>>          At Sun, 9 Oct 2011 11:21:52 +0800,
>>>          Yibin Shen wrote:
>>>
>>>              Use mmap is much simpler than local backup image, and without
>>>              any influence to consistency. but it doesn't improve
>>>              availability
>>>              while whole sheepdog cluster is die(such as some odd network
>>>              partition issue).
>>>
>>>              anyway, if no one againsts, I will try to implement it in the
>>>              near future (after we solved most stability issues)
>>>
>>>          Can we implement it as an extension of the cache mechanism?
>>>           If the
>>>          local cache file has whole data in the Sheepdog VDI, we can
>>>          regard it
>>>          as a local backup image.
>>>
>>>          Thanks,
>>>
>>>          Kazutaka
>>>
>>>
>>>      Maybe we can read-ahead in the whole data if network is not busy
>>>      gradually? When the whole image is read in, we can mark it as
>>>      'complete'.  If some time the cluster crashes, the complete image
>>>      would help the VMs on the very node to survive the crash. The
>>>      dirty bits will be flushed into cluster store in recovery stage.
>>>
>>> read-ahead whole image into memory?
>>>
>> Into file in the local disk, that is supposed to be mmapped into qemu
>> process memory.
> Is it better to mmap in the gateway sheep daemon (usually, it is a
> local sheep daemon)?  I think someone want to use Sheepdog from other
> than QEMU (e.g. iSCSI target).  In addition, we can much more freely
> modified Sheepdog server codes than QEMU client ones.
>
Hmm, yes, it is. Qemu address space just came into my mind without much 
thought.

Thanks,
Yuan