> -----Original Message----- > From: ceph-users [mailto:ceph-users-bounces@xxxxxxxxxxxxxx] On Behalf Of Dongsheng Yang > Sent: 14 February 2017 09:01 > To: Sage Weil <notifications@xxxxxxxxxx> > Cc: ceph-devel@xxxxxxxxxxxxxxx; ceph-users@xxxxxxxxxxxxxx > Subject: bcache vs flashcache vs cache tiering > > Hi Sage and all, > We are going to use SSDs for cache in ceph. But I am not sure which one is the best solution, bcache? flashcache? or cache tier? I would vote for cache tier. Being able to manage it from within Ceph, instead of having to manage X number of bcache/flashcache instances, appeals to me more. Also last time I looked Flashcache seems unmaintained and bcache might be going that way with talk of this new bcachefs. Another point to consider is that Ceph has had a lot of work done on it to ensure data consistency; I don't ever want to be in a position where I'm trying to diagnose problems that might be being caused by another layer sitting in-between Ceph and the Disk. However, I know several people on here are using bcache and potentially getting better performance than with cache tiering, so hopefully someone will give their views. > > I found there are some CAUTION in ceph.com about cache tiering. Is cache tiering is already production ready? especially for rbd. Several people have been using it in production and with Jewel I would say it's stable. There were a few gotcha's in previous releases, but they all appear to be fixed in Jewel. The main reasons for the warnings now are that unless you have a cacheable workload, performance can actually be degraded. If you can predict that say 10% of your data will be hot and provision enough SSD capacity for this hot data, then it should work really well. If you data will be uniformly random or sequential in nature, then I would steer clear, but this applies to most caching solutions albeit with maybe more graceful degradation > > thanx in advance. > Yang > _______________________________________________ > 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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