Hi Robert, Am 04.02.2016 um 00:45 schrieb Robert LeBlanc: > Once we put in our cache tier the I/O on the spindles was so low, we > just moved the journals off the SSDs onto the spindles and left the > SSD space for cache. There have been testing showing that better > performance can be achieved by putting more OSDs on an NVMe disk, but > you also have to balance that with OSDs not being evenly distributed > so some OSDs will use more space than others. Hm, maybe it was due to our very small size for the cache (only 540GB in total, limitted to max-bytes 220 GB as size=2 and your mentioned uneven distribution) we found that during times where the cache pool flushed to the storage pool client IO took a severe hit. > I probably wouldn't go more than 4 100 GB partitions, but it really > depends on the number of PGs and your data distribution. Also, even > with all the data in the cache, there is still a performance penalty > for having the caching tier vs. a native SSD pool. So if you are not > using the tiering, move to a straight SSD pool. Yes, I also have the feeling that less than 100 GB per OSD doesn't make sense. I tend to 3 OSD with about 120GB + a bit for the journals as the first "draft"-implementation. Greetings -Sascha- _______________________________________________ ceph-users mailing list ceph-users@xxxxxxxxxxxxxx http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
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