[Sheepdog] Backup/Images

[MORITA Kazutaka]

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.


Thanks,

Kazutaka