Здравствуйте! On Wed, Aug 12, 2015 at 02:30:59PM +0000, pieter.koorts wrote: > Hi Irek, > Thanks for the link. I have removed the SSD's for now and performance is up to 30MB/s on a benchmark now. To be honest, I new the Samsung SSD weren't great but did not expect them to be worse then just plain hard disks. I had the same trouble with Samsung 840 EVO 1TB. 15 of 16 disks was terribly slow (about 3000 iops and up to 200 MBps per drive). All the drives were replased by 850 EVO 250 GB and problem was fixed. My ssds had the latest firmware and was brand new at the moment of test. > Pieter > Something that's been bugging me for a while is I am trying to diagnose iowait time within KVM guests. Guests doing reads or writes tend do about 50% to 90% iowait but the host itself is only doing about 1% to 2% iowait. So the result is the guests are extremely slow. > I currently run 3x hosts each with a single SSD and single HDD OSD in cache-teir writeback mode. Although the SSD (Samsung 850 EVO 120GB) is not a great one it should at least perform reasonably compared to a hard disk and doing some direct SSD tests I get approximately 100MB/s write and 200MB/s read on each SSD. > When I run rados bench though, the benchmark starts with a not great but okay speed and as the benchmark progresses it just gets slower and slower till it's worse than a USB hard drive. The SSD cache pool is 120GB in size (360GB RAW) and in use at about 90GB. I have tried tuning the XFS mount options as well but it has had little effect. -- WBR, Max A. Krasilnikov _______________________________________________ ceph-users mailing list ceph-users@xxxxxxxxxxxxxx http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
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