[sheepdog-users] Performance Impact of Recovery

[Andrew J. Hobbs]

I'm wondering where the bottleneck is here.  I don't know if you caught 
it, but I suffered a hard fault (Dell PERC i710 decided to stop writing 
to disks) on Thursday. Rebalance of 1.7TB took roughly 1:45 hours.  If I 
recall from an earlier post, you were at a lower in-use level.  How are 
you configured?  Have you run any benchmarks in a VM to see what your 
normal performance is like?

On 03/17/2014 12:28 PM, richter at ecos.de wrote:
>> We store hash into xattr of the object while the hash is calculated.
> Hashes
>> are calculated indirectly when 1. 'dog vdi check' 2. recovery. We don't
>> calculate hash for normal read/write for better performance.
>>
> I did test it and the first recovery has taken about 9h (cluster was in
> use). I did a second recovery at the weekend when there is no load on the
> cluster and it took about 6:30h, and directly afterwards another one (so
> there should be only minimal writes between the two recoveries) and it took
> about 7h. There are currently about 160000 objects to recover.
>
> It seems that there is no speed gain by storing the hash values (which I
> can't imagine) or the hash values are not stored at all. Is it possible for
> me to verify that there are some hash values stored. Is there a simple
> command line (e.g. using getfattr)? Maybe there is some configuration error
> on my side...
>
> Thanks & Regards
>
> Gerald
>
>

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