On 07/01/2015 12:13 PM, Tuomas Juntunen wrote:
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?
Ok, so that makes more sense. The performance is still lower than
expected but maybe 3-4x rather than several orders of magnitude. My
guess is that cache tiering in it's current form probably won't help you
much unless you have a workload that fits mostly into the cache. The
promotion penalty is really high though so we likely will have to
promote much more slowly than we currently do.
Mark
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
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