[sheepdog] [PATCH] sheep: cache sha1 digest for read-only objects

[MORITA Kazutaka]

At Tue, 14 May 2013 16:22:30 +0900,
MORITA Kazutaka wrote:
> 
> At Tue, 14 May 2013 15:14:05 +0800,
> Liu Yuan wrote:
> > 
> > > The contents of read-only objects are immutable.  We can cache their
> > > sha1 digests as extended attributes for the next sha1 calculation.
> > > With this patch, I can complete 'collie vdi check' of a 4 GB snapshot
> > > volume in 0.2 seconds.
> > 
> > Any number for recovery boost?
> 
> Not tested yet.  I'll send the result later, but note that we can gain
> the performance boost only against read-only (snapshot) objects.  We

I got the similar number with vdi check when
 - the recovery is caused by node join, and
 - the joining nodes has stale objects which will be recovered to local.
This situation happens, e.g., when we reboot one of sheepdog nodes.

Of course, if the objects are not read-only, we cannot see any performance
improvement.

Thanks,

Kazutaka