Hello, On Fri, 13 Apr 2018 11:59:01 -0500 Robert Stanford wrote:
> I have 65TB stored on 24 OSDs on 3 hosts (8 OSDs per host). SSD journals > and spinning disks. Our performance before was acceptable for our purposes > - 300+MB/s simultaneous transmit and receive. Now that we're up to about > 50% of our total storage capacity (65/120TB, say), the write performance is > still ok, but the read performance is unworkable (35MB/s!) > As always, full details. Versions, HW, what SSDs, what HDDs and how connected, what FS on the OSDs, etc. > I am using index sharding, with 256 shards. I don't see any CPUs > saturated on any host (we are using radosgw by the way, and the load is > light there as well). The hard drives don't seem to be *too* busy (a > random OSD shows ~10 wa in top). The network's fine, as we were doing much > better in terms of speed before we filled up. > top is an abysmal tool for these things, use atop in a big terminal window on all 3 hosts for full situational awareness. "iostat -x 3" might do in a pinch for IO related bits, too. Keep in mind that a single busy OSD will drag the performance of the whole cluster down. Other things to check and verify: 1. Are the OSDs reasonably balanced PG wise? 2. How fragmented are the OSD FS? 3. Is a deep scrub running during the low performance times? 4. Have you run out of RAM for the pagecache and more importantly the SLAB for dir_entries due to the number of objects (files)? If so reads will require many more disk accesses than otherwise. This is a typical wall to run into and can be mitigated by more RAM and sysctl tuning. Christian > Is there anything we can do about this, short of replacing hardware? Is > it really a limitation of Ceph that getting 50% full makes your cluster > unusable? Index sharding has seemed to not help at all (I did some > benchmarking, with 128 shards and then 256; same result each time.) > > Or are we out of luck? -- Christian Balzer Network/Systems Engineer ch...@gol.com Rakuten Communications _______________________________________________ ceph-users mailing list ceph-users@lists.ceph.com http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
