Hi Yes, the OSD's are on spinning disks and we have 18 SSD's for journal, one SSD for two OSD's The OSD's are: Model Family: Seagate Barracuda 7200.14 (AF) Device Model: ST2000DM001-1CH164 What I've understood the journals are not used as read cache at all, just for writing. Would SSD based cache pool be viable solution here? Br, T -----Original Message----- From: Mark Nelson [mailto:mnelson@xxxxxxxxxx] Sent: 1. heinäkuuta 2015 13:58 To: Tuomas Juntunen; ceph-users@xxxxxxxxxxxxxx Subject: Re: Very low 4k randread performance ~1000iops On 06/30/2015 10:42 PM, Tuomas Juntunen wrote: > Hi > > For seq reads here's the latencies: > lat (usec) : 2=0.01%, 10=0.01%, 20=0.01%, 50=0.02%, 100=0.03% > lat (usec) : 250=1.02%, 500=87.09%, 750=7.47%, 1000=1.50% > lat (msec) : 2=0.76%, 4=1.72%, 10=0.19%, 20=0.19% > > Random reads: > lat (usec) : 10=0.01% > lat (msec) : 2=0.01%, 4=0.01%, 10=0.02%, 20=0.03%, 50=0.55% > lat (msec) : 100=99.31%, 250=0.08% > > 100msecs seems a lot to me. It is, but what's more interesting imho is that it's so consistent. You don't have some ops completing fast and other ones completing slowly holding everything up. It's like the OSDs are simply overloaded with concurrent IOs and everything is waiting. Maybe I'm confused, are your OSDs on SSDs? Are there spinning disks involved? If so, what model(s)? You might want to use "collectl -sD -oT" on one of the OSD nodes during the test and see what the IO to the disk looks like during random reads and the especially with the svctime for the disks is like. Mark > > Br,T > > -----Original Message----- > From: Mark Nelson [mailto:mnelson@xxxxxxxxxx] > Sent: 30. kesäkuuta 2015 22:01 > To: Tuomas Juntunen; ceph-users@xxxxxxxxxxxxxx > Subject: Re: Very low 4k randread performance ~1000iops > > Seems reasonable. What's the latency distribution look like in your > fio output file? Would be useful to know if it's universally slow or > if some ops are taking much longer to complete than others. > > Mark > > On 06/30/2015 01:27 PM, Tuomas Juntunen wrote: >> I created a file which has the following parameters >> >> >> [random-read] >> rw=randread >> size=128m >> directory=/root/asd >> ioengine=libaio >> bs=4k >> #numjobs=8 >> iodepth=64 >> >> >> Br,T >> -----Original Message----- >> From: ceph-users [mailto:ceph-users-bounces@xxxxxxxxxxxxxx] On Behalf >> Of Mark Nelson >> Sent: 30. kesäkuuta 2015 20:55 >> To: ceph-users@xxxxxxxxxxxxxx >> Subject: Re: Very low 4k randread performance ~1000iops >> >> Hi Tuomos, >> >> Can you paste the command you ran to do the test? >> >> Thanks, >> Mark >> >> On 06/30/2015 12:18 PM, Tuomas Juntunen wrote: >>> Hi >>> >>> It?s not probably hitting the disks, but that really doesn?t matter. >>> The point is we have very responsive VM?s while writing and that is >>> what the users will see. >>> >>> The iops we get with sequential read is good, but the random read is >>> way too low. >>> >>> Is using SSD?s as OSD?s the only way to get it up? or is there some >>> tunable which would enhance it? I would assume Linux caches reads in >>> memory and serves them from there, but atleast now we don?t see it. >>> >>> Br, >>> >>> Tuomas >>> >>> *From:*Somnath Roy [mailto:Somnath.Roy@xxxxxxxxxxx] >>> *Sent:* 30. kesäkuuta 2015 19:24 >>> *To:* Tuomas Juntunen; 'ceph-users' >>> *Subject:* RE: Very low 4k randread performance >>> ~1000iops >>> >>> Break it down, try fio-rbd to see what is the performance you getting.. >>> >>> But, I am really surprised you are getting > 100k iops for write, >>> did you check it is hitting the disks ? >>> >>> Thanks & Regards >>> >>> Somnath >>> >>> *From:*ceph-users [mailto:ceph-users-bounces@xxxxxxxxxxxxxx] *On >>> Behalf Of *Tuomas Juntunen >>> *Sent:* Tuesday, June 30, 2015 8:33 AM >>> *To:* 'ceph-users' >>> *Subject:* Very low 4k randread performance ~1000iops >>> >>> Hi >>> >>> I have been trying to figure out why our 4k random reads in VM?s are >>> so bad. I am using fio to test this. >>> >>> Write : 170k iops >>> >>> Random write : 109k iops >>> >>> Read : 64k iops >>> >>> Random read : 1k iops >>> >>> Our setup is: >>> >>> 3 nodes with 36 OSDs, 18 SSD?s one SSD for two OSD?s, each node has >>> 64gb mem & 2x6core cpu?s >>> >>> 4 monitors running on other servers >>> >>> 40gbit infiniband with IPoIB >>> >>> Openstack : Qemu-kvm for virtuals >>> >>> Any help would be appreciated >>> >>> Thank you in advance. >>> >>> Br, >>> >>> Tuomas >>> >>> -------------------------------------------------------------------- >>> - >>> - >>> -- >>> >>> >>> PLEASE NOTE: The information contained in this electronic mail >>> message is intended only for the use of the designated recipient(s) >>> named > above. >>> If the reader of this message is not the intended recipient, you are >>> hereby notified that you have received this message in error and >>> that any review, dissemination, distribution, or copying of this >>> message is strictly prohibited. If you have received this >>> communication in error, please notify the sender by telephone or >>> e-mail (as shown >>> above) immediately and destroy any and all copies of this message in >>> your possession (whether hard copies or electronically stored copies). >>> >>> >>> >>> _______________________________________________ >>> 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 >> > _______________________________________________ ceph-users mailing list ceph-users@xxxxxxxxxxxxxx http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
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