One scenario I can offer here as it relates to powercut/hard shutdown. I had my data center get struck by lightning very early on in my Ceph lifespan when I was testing and evaluating.
I had 8 OSD’s on 8 hosts, and each OSD was a RAID0 (single) vd on my LSI RAID controller. On the RAID controller, I did not have a BBU. (mistake 1) On the disks, I was using on-disk cache (pdcache), as well as write back cache at the controller level. (mistake 2, mistake 3) It was a learning experience, as it corrupted leveldb on 6/8 OSD’s, as the on-disk cache had partially written writes to persistent storage. So moral of the story was to make sure pdcache is configured to off, if expecting power failures. > $ sudo /opt/MegaRAID/storcli/storcli64 /c0 add vd type=raid0 drives=252:0 > pdcache=off And BBU’s would also increase likelihood of writes not going missing. Reed > On May 2, 2017, at 3:12 AM, Tomáš Kukrál <[email protected]> wrote: > > > > Hi, > It really depends on type of power failure ... > > Normal poweroff of the cluster is fine ... I've been managing large cluster > and we were forced to do total poweroff twice a year. It was working fine: we > just safely unmounted all clients, then set noout flag and powered machines > down. > > Powercut (hard shutdown) can be a big problem and I would expected problems > here. > > Tom > > On 04-22 05:04, Santu Roy wrote: >> Hi >> >> I am very new to Ceph. Studding for few days for a deployment of Ceph >> cluster. I am going to deploy ceph in a small data center where power >> failure is a big problem. we have single power supply, Single ups and a >> stand by generator. so what happend if all node down due to power failure? >> will it create any problem to restart service when power restore? >> >> looking for your suggestion.. >> >> -- >> >> *Regards*Santu Roy > >> _______________________________________________ >> ceph-users mailing list >> [email protected] >> http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com > > _______________________________________________ > ceph-users mailing list > [email protected] > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
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