On 03/31/2018 03:24 PM, Mark Nelson wrote: >> 1. Completely new users may think that bluestore defaults are fine and >> waste all that RAM in their machines. > > What does "wasting" RAM mean in the context of a node running ceph? Are > you upset that other applications can't come in and evict bluestore > onode, OMAP, or object data from cache? I think he thought of your #1 Unless I am mistaken, with bluestore, you allocate some cache per OSD, and the OSD won't use more, even if there is free memory laying around Thus, a "waste" of ram >> 2. Having a per OSD cache is inefficient compared to a common cache like >> pagecache, since an OSD that is busier than others would benefit from a >> shared cache more. > > It's only "inefficient" if you assume that using the pagecache, and more > generally, kernel syscalls, is free. Yes the pagecache is convenient > and yes it gives you a lot of flexibility, but you pay for that > flexibility if you are trying to do anything fast. I think he thought of your #2 "Inefficient" because each OSDs have a fixed cache size, unrelated to their real usage To me, "flawed" is a bit extreme, bluestore is a good piece of work, even if there is still place for improvements; _______________________________________________ ceph-users mailing list ceph-users@xxxxxxxxxxxxxx http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
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