> Personally I am not worried too much about the hypervisor - hypervisor > traffic as I am using a dedicated infiniband network for storage. > It is not used for the guest to guest or the internet traffic or anything > else. I would like to decrease or at least smooth out the traffic peaks > between the hypervisors and the SAS/SATA osd storage servers. > I guess the ssd cache pool would enable me to do that as the eviction rate > should be more structured compared to the random io writes that guest vms > generate. Sounds reasonable
>>I'm very interested in the effect of caching pools in combination with >>running VMs on them so I'd be happy to hear what you find ;) > I will give it a try and share back the results when we get the ssd kit. Excellent, looking forward to it. >> As a side note: Running OSDs on hypervisors would not be my preferred choice >> since hypervisor load might impact Ceph performance. > Do you think it is not a good idea even if you have a lot of cores on the > hypervisors? > Like 24 or 32 per host server? > According to my monitoring, our osd servers are not that stressed and > generally have over 50% of free cpu power. The number of cores do not really matter if they are all busy ;) I honestly do not know how Ceph behaves when it is CPU starved but I guess it might not be pretty. Since your whole environment will be crumbling down if your storage becomes unavailable it is not a risk I would take lightly. Cheers, Robert van Leeuwen
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