Hi, I forgot to mention: while I am seeing these writes in iotop and /proc/diskstats for the hdd's, I am -not- seeing any writes in "rados df" for the pool residing on these disks. There is only one pool active on the hdd's and according to rados df it is getting zero writes when I'm just reading big files from cephfs. So apparently the osd's are doing some non-trivial amount of writing on their own behalf. What could it be? Thanks, Erik. On 03/16/2015 10:26 PM, Erik Logtenberg wrote: > Hi, > > I am getting relatively bad performance from cephfs. I use a replicated > cache pool on ssd in front of an erasure coded pool on rotating media. > > When reading big files (streaming video), I see a lot of disk i/o, > especially writes. I have no clue what could cause these writes. The > writes are going to the hdd's and they stop when I stop reading. > > I mounted everything with noatime and nodiratime so it shouldn't be > that. On a related note, the Cephfs metadata is stored on ssd too, so > metadata-related changes shouldn't hit the hdd's anyway I think. > > Any thoughts? How can I get more information about what ceph is doing? > Using iotop I only see that the osd processes are busy but it doesn't > give many hints as to what they are doing. > > Thanks, > > Erik. > _______________________________________________ > 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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