Hey all,
It has been a while since the last thread performance related on the ML :p
I’ve been running some experiment to see how much I can get from an SSD on a
Ceph cluster.
To achieve that I did something pretty simple:
* Debian wheezy 7.6
* kernel from debian 3.14-0.bpo.2-amd64
* 1 cluster, 3 mons (i’d like to keep this realistic since in a real deployment
i’ll use 3)
* 1 OSD backed by an SSD (journal and osd data on the same device)
* 1 replica count of 1
* partitions are perfectly aligned
* io scheduler is set to noon but deadline was showing the same results
* no updatedb running
About the box:
* 32GB of RAM
* 12 cores with HT @ 2,4 GHz
* WB cache is enabled on the controller
* 10Gbps network (doesn’t help here)
The SSD is a 200G Intel DC S3700 and is capable of delivering around 29K iops
with random 4k writes (my fio results)
As a benchmark tool I used fio with the rbd engine (thanks deutsche telekom
guys!).
O_DIECT and D_SYNC don’t seem to be a problem for the SSD:
# dd if=/dev/urandom of=rand.file bs=4k count=65536
65536+0 records in
65536+0 records out
268435456 bytes (268 MB) copied, 29.5477 s, 9.1 MB/s
# du -sh rand.file
256M rand.file
# dd if=rand.file of=/dev/sdo bs=4k count=65536 oflag=dsync,direct
65536+0 records in
65536+0 records out
268435456 bytes (268 MB) copied, 2.73628 s, 98.1 MB/s
See my ceph.conf:
[global]
auth cluster required = cephx
auth service required = cephx
auth client required = cephx
fsid = 857b8609-8c9b-499e-9161-2ea67ba51c97
osd pool default pg num = 4096
osd pool default pgp num = 4096
osd pool default size = 2
osd crush chooseleaf type = 0
debug lockdep = 0/0
debug context = 0/0
debug crush = 0/0
debug buffer = 0/0
debug timer = 0/0
debug journaler = 0/0
debug osd = 0/0
debug optracker = 0/0
debug objclass = 0/0
debug filestore = 0/0
debug journal = 0/0
debug ms = 0/0
debug monc = 0/0
debug tp = 0/0
debug auth = 0/0
debug finisher = 0/0
debug heartbeatmap = 0/0
debug perfcounter = 0/0
debug asok = 0/0
debug throttle = 0/0
[mon]
mon osd down out interval = 600
mon osd min down reporters = 13
[mon.ceph-01]
host = ceph-01
mon addr = 172.20.20.171
[mon.ceph-02]
host = ceph-02
mon addr = 172.20.20.172
[mon.ceph-03]
host = ceph-03
mon addr = 172.20.20.173
debug lockdep = 0/0
debug context = 0/0
debug crush = 0/0
debug buffer = 0/0
debug timer = 0/0
debug journaler = 0/0
debug osd = 0/0
debug optracker = 0/0
debug objclass = 0/0
debug filestore = 0/0
debug journal = 0/0
debug ms = 0/0
debug monc = 0/0
debug tp = 0/0
debug auth = 0/0
debug finisher = 0/0
debug heartbeatmap = 0/0
debug perfcounter = 0/0
debug asok = 0/0
debug throttle = 0/0
[osd]
osd mkfs type = xfs
osd mkfs options xfs = -f -i size=2048
osd mount options xfs = rw,noatime,logbsize=256k,delaylog
osd journal size = 20480
cluster_network = 172.20.20.0/24
public_network = 172.20.20.0/24
osd mon heartbeat interval = 30
# Performance tuning
filestore merge threshold = 40
filestore split multiple = 8
osd op threads = 8
# Recovery tuning
osd recovery max active = 1
osd max backfills = 1
osd recovery op priority = 1
debug lockdep = 0/0
debug context = 0/0
debug crush = 0/0
debug buffer = 0/0
debug timer = 0/0
debug journaler = 0/0
debug osd = 0/0
debug optracker = 0/0
debug objclass = 0/0
debug filestore = 0/0
debug journal = 0/0
debug ms = 0/0
debug monc = 0/0
debug tp = 0/0
debug auth = 0/0
debug finisher = 0/0
debug heartbeatmap = 0/0
debug perfcounter = 0/0
debug asok = 0/0
debug throttle = 0/0
Disabling all debugging made me win 200/300 more IOPS.
See my fio template:
[global]
#logging
#write_iops_log=write_iops_log
#write_bw_log=write_bw_log
#write_lat_log=write_lat_lo
time_based
runtime=60
ioengine=rbd
clientname=admin
pool=test
rbdname=fio
invalidate=0 # mandatory
#rw=randwrite
rw=write
bs=4k
#bs=32m
size=5G
group_reporting
[rbd_iodepth32]
iodepth=32
direct=1
See my rio output:
rbd_iodepth32: (g=0): rw=write, bs=4K-4K/4K-4K/4K-4K, ioengine=rbd, iodepth=32
fio-2.1.11-14-gb74e
Starting 1 process
rbd engine: RBD version: 0.1.8
Jobs: 1 (f=1): [W(1)] [100.0% done] [0KB/12876KB/0KB /s] [0/3219/0 iops] [eta
00m:00s]
rbd_iodepth32: (groupid=0, jobs=1): err= 0: pid=32116: Thu Aug 28 00:28:26 2014
write: io=771448KB, bw=12855KB/s, iops=3213, runt= 60010msec
slat (usec): min=42, max=1578, avg=66.50, stdev=16.96
clat (msec): min=1, max=28, avg= 9.85, stdev= 1.48
lat (msec): min=1, max=28, avg= 9.92, stdev= 1.47
clat percentiles (usec):
| 1.00th=[ 6368], 5.00th=[ 8256], 10.00th=[ 8640], 20.00th=[ 9152],
| 30.00th=[ 9408], 40.00th=[ 9664], 50.00th=[ 9792], 60.00th=[10048],
| 70.00th=[10176], 80.00th=[10560], 90.00th=[10944], 95.00th=[11456],
| 99.00th=[13120], 99.50th=[16768], 99.90th=[25984], 99.95th=[27008],
| 99.99th=[28032]
bw (KB /s): min=11864, max=13808, per=100.00%, avg=12864.36, stdev=407.35
lat (msec) : 2=0.03%, 4=0.54%, 10=59.79%, 20=39.24%, 50=0.41%
cpu : usr=19.15%, sys=4.69%, ctx=326309, majf=0, minf=426088
IO depths : 1=0.1%, 2=0.1%, 4=0.1%, 8=0.1%, 16=33.9%, 32=66.1%, >=64=0.0%
submit : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0%
complete : 0=0.0%, 4=99.6%, 8=0.4%, 16=0.1%, 32=0.1%, 64=0.0%, >=64=0.0%
issued : total=r=0/w=192862/d=0, short=r=0/w=0/d=0
latency : target=0, window=0, percentile=100.00%, depth=32
Run status group 0 (all jobs):
WRITE: io=771448KB, aggrb=12855KB/s, minb=12855KB/s, maxb=12855KB/s,
mint=60010msec, maxt=60010msec
Disk stats (read/write):
dm-1: ios=0/49, merge=0/0, ticks=0/12, in_queue=12, util=0.01%,
aggrios=0/22, aggrmerge=0/27, aggrticks=0/12, aggrin_queue=12, aggrutil=0.01%
sda: ios=0/22, merge=0/27, ticks=0/12, in_queue=12, util=0.01%
I tried to tweak several parameters like:
filestore_wbthrottle_xfs_ios_start_flusher = 10000
filestore_wbthrottle_xfs_ios_hard_limit = 10000
filestore_wbthrottle_btrfs_ios_start_flusher = 10000
filestore_wbthrottle_btrfs_ios_hard_limit = 10000
filestore queue max ops = 2000
But didn’t any improvement.
Then I tried other things:
* Increasing the io_depth up to 256 or 512 gave me between 50 to 100 more IOPS
but it’s not a realistic workload anymore and not that significant.
* adding another SSD for the journal, still getting 3,2K IOPS
* I tried with rbd bench and I also got 3K IOPS
* I ran the test on a client machine and then locally on the server, still
getting 3,2K IOPS
* put the journal in memory, still getting 3,2K IOPS
* with 2 clients running the test in parallel I got a total of 3,6K IOPS but I
don’t seem to be able to go over
* I tried is to add another OSD to that SSD, so I had 2 OSD and 2 journals on 1
SSD, got 4,5K IOPS YAY!
Given the results of the last time it seems that something is limiting the
number of IOPS per OSD process.
Running the test on a client or locally didn’t show any difference.
So it looks to me that there is some contention within Ceph that might cause
this.
I also ran perf and looked at the output, everything looks decent, but someone
might want to have a look at it :).
We have been able to reproduce this on 3 distinct platforms with some
deviations (because of the hardware) but the behaviour is the same.
Any thoughts will be highly appreciated, only getting 3,2k out of an 29K IOPS
SSD is a bit frustrating :).
Cheers.
––––
Sébastien Han
Cloud Architect
"Always give 100%. Unless you're giving blood."
Phone: +33 (0)1 49 70 99 72
Mail: sebastien....@enovance.com
Address : 11 bis, rue Roquépine - 75008 Paris
Web : www.enovance.com - Twitter : @enovance
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