On Tue, Oct 2, 2018 at 6:28 PM <jesper@xxxxxxxx> wrote: > > Hi. > > Based on some recommendations we have setup our CephFS installation using > bluestore*. We're trying to get a strong replacement for "huge" xfs+NFS > server - 100TB-ish size. > > Current setup is - a sizeable Linux host with 512GB of memory - one large > Dell MD1200 or MD1220 - 100TB + a Linux kernel NFS server. > > Since our "hot" dataset is < 400GB we can actually serve the hot data > directly out of the host page-cache and never really touch the "slow" > underlying drives. Except when new bulk data are written where a Perc with > BBWC is consuming the data. > > In the CephFS + Bluestore world, Ceph is "deliberatly" bypassing the host > OS page-cache, so even when we have 4-5 x 256GB memory** in the OSD hosts > it is really hard to create a synthetic test where they hot data does not > end up being read out of the underlying disks. Yes, the > client side page cache works very well, but in our scenario we have 30+ > hosts pulling the same data over NFS. Are you finding that the OSDs use lots of memory but you're still hitting disk, or just that the OSDs aren't using up all the available memory? Unlike the page cache, the OSDs will not use all the memory in your system by default, you have to tell them how much to use (http://docs.ceph.com/docs/mimic/rados/configuration/bluestore-config-ref/#cache-size) John > Is bluestore just a "bad fit" .. Filestore "should" do the right thing? Is > the recommendation to make an SSD "overlay" on the slow drives? > > Thoughts? > > Jesper > > * Bluestore should be the new and shiny future - right? > ** Total mem 1TB+ > > > > _______________________________________________ > 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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