Hello, On Mon, 22 Aug 2016 14:33:51 +0200 Florent B wrote: > Hi, > > I'm looking for informations about cache-tiering. > Have you searched the ML archives, including my "Cache tier operation clarifications" thread? > I can't find if pools used as "hot storage" in cache-tiering should be > replicated or could be set with size=1 ? > This particular question I remember answering at least once here. > As I understand documentation, data written to hot storage is > immediately written to cold storage, so size=1 for hot storage should be > fine. > Where do you get that idea from? Please cite the source. If this were the case, where would be the speed advantage over your default pool? Journaling kinda resembles this behavior, cache tiering most definitely not. A cache pool is a regular Ceph pool, so it needs: a) journals (with filestore, for the time being) b) to be replicated at level you feel comfortable with. Whether b) is fine with 2 or should be 3 depends on the SSDs/NVMEs your using, the monitoring you're doing and of course your budget. A replication of 2 also will be faster than 3, but given that most if not ALL your hot objects will be in your cache pool and may NEVER be written to cold storage ever that shouldn't be your primary concern. Christian > Thank you. > > Florent > > _______________________________________________ > ceph-users mailing list > ceph-users@xxxxxxxxxxxxxx > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com > -- Christian Balzer Network/Systems Engineer chibi@xxxxxxx Global OnLine Japan/Rakuten Communications http://www.gol.com/ _______________________________________________ ceph-users mailing list ceph-users@xxxxxxxxxxxxxx http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
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