Hi, It is my experience with Bluestore that even if you put DB/WAL on a very fast SSD (NVME in my case), the OSD will still refuse to write faster than the storage device (HDD) can write on average. This is a bummer because the behavior is very different from Filestore, which could buffer write bursts on SSD, defer and write them to HDD later on. Having DB/WAL on SSD still helps with general latency, though. With regards to SSD cache, putting an SSD cache tier with Ceph is possible, but be prepared that it doesn't quite work the way you would expect it to, that its performance is very highly dependent on your workload, and that it may cause sudden issues: for example, with 16.2.x my VMs would randomly lose access to their RBD images during intense writes through a cache tier. Putting a cache tier for an OSD device with bcache, dm-cache, etc may be a better and more stable option, although it is unlikely that you will be able to automate this with Ceph toolset. Best regards, Z On Fri, Oct 22, 2021 at 12:30 PM Mevludin Blazevic <mblazevic@xxxxxxxxxxxxxx> wrote: > Dear Ceph users, > > I have a small Ceph cluster where each host consist of a small amount of > SSDs and a larger number of HDDs. Is there a way to use the SSDs as > performance optimization such as putting OSD Journals to the SSDs and/or > using SSDs for caching? > > Best regards, > Mevludin > > -- > Mevludin Blazevic, M.Sc. > > University of Koblenz-Landau > Computing Centre (GHRKO) > Universitaetsstrasse 1 > D-56070 Koblenz, Germany > Room A023 > Tel: +49 261/287-1326 > > _______________________________________________ > ceph-users mailing list -- ceph-users@xxxxxxx > To unsubscribe send an email to ceph-users-leave@xxxxxxx > _______________________________________________ ceph-users mailing list -- ceph-users@xxxxxxx To unsubscribe send an email to ceph-users-leave@xxxxxxx
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