Reed Dier <reed.dier@xxxxxxxxxxx> writes: > I don't have any performance bits to offer, but I do have one experiential bit to offer. > > My initial ceph deployment was on existing servers, that had LSI raid controllers (3108 specifically). > We created R0 vd's for each disk, and had BBUs so were using write back caching. > The big problem that arose was the pdcache value, which in my case defaults to on. > > We had a lightning strike that took out the datacenter, and we lost 21/24 OSDs. > Granted, this was back in XFS-on-filestore days, but this was a painful lesson learned. > It was narrowed down to the pdcache and not to the raid controller caching functions after carrying out some power-loss scenarios after the incident. It's not a 100% clear to me, but is the pdcache the same as the disk internal (non battery backed up) cache? As we are located very nearby the hydropower plant, we actually connect each server individually to an UPS. Our original motivation was mainly to cut off over voltage, but it has the nice side effect of having another battery buffer on servers. -- Sustainable and modern Infrastructures by ungleich.ch _______________________________________________ ceph-users mailing list -- ceph-users@xxxxxxx To unsubscribe send an email to ceph-users-leave@xxxxxxx
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