Are these single threaded writes that you are referring to?  It certainly 
appears so from the thread, but I thought it would be good to confirm that 
before digging in further.


David Byte
Sr. Technology Strategist
SCE Enterprise Linux
SCE Enterprise Storage
Alliances and SUSE Embedded
db...@suse.com<mailto:db...@suse.com>
918.528.4422

From: ceph-users <ceph-users-boun...@lists.ceph.com> on behalf of Joe Comeau 
<joe.com...@hli.ubc.ca>
Date: Friday, August 31, 2018 at 1:07 PM
To: "ceph-users@lists.ceph.com" <ceph-users@lists.ceph.com>, Peter Eisch 
<peter.ei...@virginpulse.com>
Subject: Re: [ceph-users] cephfs speed

Are you using bluestore OSDs ?

if so my thought process on this is what we are having an issue with is caching 
and bluestore

see the thread on bluestore caching
"Re: [ceph-users] Best practices for allocating memory to bluestore cache"


before when we were on Jewel and filestore we could get a much better sustained 
write
Now on bluestore we are not getting more than a sustained 2GB file write before 
it drastically slows down
Then it fluctuates from 0kb/s to 100MB/s and back and forth as it is writing

Thanks Joe

>>> Peter Eisch <peter.ei...@virginpulse.com> 8/31/2018 10:31 AM >>>
[replying to myself]

I set aside cephfs and created an rbd volume. I get the same splotchy 
throughput with rbd as I was getting with cephfs. (image attached)

So, withdrawing this as a question here as a cephfs issue.

#backingout

peter

Peter Eisch​




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On 8/30/18, 12:25 PM, "Peter Eisch" <peter.ei...@virginpulse.com> wrote:

Thanks for the thought. It’s mounted with this entry in fstab (one line, if 
email wraps it):

cephmon-s01,cephmon-s02,cephmon-s03:/ /loam ceph 
noauto,name=clientname,secretfile=/etc/ceph/secret,noatime,_netdev 0 2

Pretty plain, but I'm open to tweaking!

peter

From: Gregory Farnum <gfar...@redhat.com>
Date: Thursday, August 30, 2018 at 11:47 AM
To: Peter Eisch <peter.ei...@virginpulse.com>
Cc: "ceph-users@lists.ceph.com" <ceph-users@lists.ceph.com>
Subject: Re: [ceph-users] cephfs speed

How are you mounting CephFS? It may be that the cache settings are just set 
very badly for a 10G pipe. Plus rados bench is a very parallel large-IO 
benchmark and many benchmarks you might dump into a filesystem are definitely 
not.
-Greg

On Thu, Aug 30, 2018 at 7:54 AM Peter Eisch 
<mailto:peter.ei...@virginpulse.com> wrote:
Hi,

I have a cluster serving cephfs and it works. It’s just slow. Client is using 
the kernel driver. I can ‘rados bench’ writes to the cephfs_data pool at wire 
speeds (9580Mb/s on a 10G link) but when I copy data into cephfs it is rare to 
get above 100Mb/s. Large file writes may start fast (2Gb/s) but within a minute 
slows. In the dashboard at the OSDs I get lots of triangles (it doesn't stream) 
which seems to be lots of starts and stops. By contrast the graphs show 
constant flow when using 'rados bench.'

I feel like I'm missing something obvious. What can I do to help diagnose this 
better or resolve the issue?

Errata:
Version: 12.2.7 (on everything)
mon: 3 daemons, quorum cephmon-s01,cephmon-s03,cephmon-s02
mgr: cephmon-s02(active), standbys: cephmon-s01, cephmon-s03
mds: cephfs1-1/1/1 up {0=cephmon-s02=up:active}, 2 up:standby
osd: 70 osds: 70 up, 70 in
rgw: 3 daemons active

rados bench summary:
Total time run: 600.043733
Total writes made: 167725
Write size: 4194304
Object size: 4194304
Bandwidth (MB/sec): 1118.09
Stddev Bandwidth: 7.23868
Max bandwidth (MB/sec): 1140
Min bandwidth (MB/sec): 1084
Average IOPS: 279
Stddev IOPS: 1
Max IOPS: 285
Min IOPS: 271
Average Latency(s): 0.057239
Stddev Latency(s): 0.0354817
Max latency(s): 0.367037
Min latency(s): 0.0120791

peter


Peter Eisch​











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