[sheepdog-users] Performance Impact of Recovery

[richter at ecos.de]

Hi,













I have about 600GB in my sheepdog cluster. A recovery of one node has
started today morning and it is at 20% after 2h, so it will still take
another 8h. I would like to put more vm's in the cluster, but then recovery
would take even longer.
















During recovery there is a lot of disk read activity on the recovery node
and on other nodes, because (as far as I understand) hashes for the data
blocks are computed and compared. This disk activity is so heavy, that other
vm's that are still running out of qcow2 files, have a notable performance
impact. 
















If I imagine I have more data in the sheepdog cluster and recovery might
take 2 days, all my vm's running slow for two days, this will not be
accepted by my users, but sometime a recovery might be necessary (e.g.
server reboot or sheep crash like today morning).
















So the question is how can this recovery process speed up? 
















>From my current knowledge (which is not too deep), the only idea would be to
calculate the data block hashes during storing of the data block and compare
only stored hashes. Would this be possible/make sense or is there a better
solution?
















I really find sheepdog a great solution and I appreciate all your work you
put into sheepdog and I really like to use it in production, but recovery
performance really is an issue for me.
















Thanks & Regards
















Gerald
















 








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