I had great results from the older 530 series too. In this case however, the SSDs were only used for journals and I don't know if ceph-osd sends TRIM to the drive in the process of journaling over a block device. They were also under-subscribed, with just 3 x 10G partitions out of 240 GB raw capacity. I did a manual trim, but it hasn't changed anything. I'm still having fun with the configuration so I'll be able to use Mike Dawson's suggested tools to check for latencies. On Nov 6, 2013, at 11:35 PM, james@xxxxxxxxxxxx wrote: > On 2013-11-06 20:25, Mike Dawson wrote: > >> We just fixed a performance issue on our cluster related to spikes of high latency on some of our SSDs used for osd journals. In our case, the slow SSDs showed spikes of 100x higher latency than expected. > > > Many SSDs show this behaviour when 100% provisioned and/or never TRIM'd, since the pool of ready erased cells is quickly depleted under steady write workload, so it has to wait for cells to charge to accommodate the write. > > The Intel 3700 SSDs look to have some of the best consistency ratings of any of the more reasonably priced drives at the moment, and good IOPS too: > > http://www.intel.com/content/www/us/en/solid-state-drives/solid-state-drives-dc-s3700-series.html > > Obviously the quoted IOPS numbers are dependent on quite a deep queue mind. > > There is a big range of performance in the market currently; some Enterprise SSDs are quoted at just 4,000 IOPS yet cost as many pounds! > > > _______________________________________________ > 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
 |