Hi Nick, Am 11.03.2015 um 10:52 schrieb Nick Fisk: > Hi Stefan, > > If the majority of your hot data fits on the cache tier you will see quite a > marked improvement in read performance I don't have writes ;-) just around 5%. 95% are writes. > and similar write performance > (assuming you would have had your hdds backed by SSD journals). similar write performance of SSD cache tier or HDD "backend" tier? I'm mainly interested in a writeback mode. > However for data that is not in the cache tier you will get 10-20% less read > performance and anything up to 10x less write performance. This is because a > cache write miss has to read the entire object from the backing store into > the cache and then modify it. > > The read performance degradation will probably be fixed in Hammer with proxy > reads, but writes will most likely still be an issue. Why is writing to the HOT part so slow? Stefan > Nick > > >> -----Original Message----- >> From: ceph-users [mailto:ceph-users-bounces@xxxxxxxxxxxxxx] On Behalf Of >> Stefan Priebe - Profihost AG >> Sent: 11 March 2015 07:27 >> To: ceph-users@xxxxxxxxxxxxxx >> Subject: Firefly Tiering >> >> Hi, >> >> has anybody successfully tested tiering while using firefly? How much does > it >> impact performance vs. a normal pool? I mean is there any difference >> between a full SSD pool und a tiering SSD pool with SATA Backend? >> >> Greets, >> Stefan >> _______________________________________________ >> ceph-users mailing list >> ceph-users@xxxxxxxxxxxxxx >> http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com > > > > _______________________________________________ ceph-users mailing list ceph-users@xxxxxxxxxxxxxx http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
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