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Hi Mark,
having 2 node for testing allow me to downgrade the replication
to 2x (till the production).
SSD have the following product details:
- sequential read: 540MB/sec
- sequential write: 520MB/sec
As you state my sequential write should be:
~600 * 2 (copies) * 2 (journal write per copy) / 8 (ssds) =
~225,25MB/s
If you think that 2 copies should be simultaneously on
different cards/networks/nodes my calculation are:
~600 * 2 (journal write per copy) / 8 (ssds) = ~112,625MB/s
So yes, I think that they are
terrible low (but maybe I miss something), about 20,8% of the
theorical speed of an SSD.
Sequential Read are quite low too.
Maybe only Random Read is good.
Any suggestion?
Il 22/06/2017 19:41, Mark Nelson ha
scritto:
Hello
Massimiliano,
Based on the configuration below, it appears you have 8 SSDs total
(2 nodes with 4 SSDs each)?
I'm going to assume you have 3x replication and are you using
filestore, so in reality you are writing 3 copies and doing full
data journaling for each copy, for 6x writes per client write.
Taking this into account, your per-SSD throughput should be
somewhere around:
Sequential write:
~600 * 3 (copies) * 2 (journal write per copy) / 8 (ssds) =
~450MB/s
Sequential read
~3000 / 8 (ssds) = ~375MB/s
Random read
~3337 / 8 (ssds) = ~417MB/s
These numbers are pretty reasonable for SATA based SSDs, though
the read throughput is a little low. You didn't include the model
of SSD, but if you look at Intel's DC S3700 which is a fairly
popular SSD for ceph:
https://www.intel.com/content/www/us/en/solid-state-drives/ssd-dc-s3700-spec.html
Sequential read is up to ~500MB/s and Sequential write speeds up
to 460MB/s. Not too far off from what you are seeing. You might
try playing with readahead on the OSD devices to see if that
improves things at all. Still, unless I've missed something these
numbers aren't terrible.
Mark
On 06/22/2017 12:19 PM, Massimiliano Cuttini wrote:
Hi everybody,
I want to squeeze all the performance of CEPH (we are using
jewel 10.2.7).
We are testing a testing environment with 2 nodes having the
same
configuration:
* CentOS 7.3
* 24 CPUs (12 for real in hyper threading)
* 32Gb of RAM
* 2x 100Gbit/s ethernet cards
* 2x OS dedicated in raid SSD Disks
* 4x OSD SSD Disks SATA 6Gbit/s
We are already expecting the following bottlenecks:
* [ SATA speed x n° disks ] = 24Gbit/s
* [ Networks speed x n° bonded cards ] = 200Gbit/s
So the minimum between them is 24 Gbit/s per node (not taking in
account
protocol loss).
24Gbit/s per node x2 = 48Gbit/s of maximum hypotetical theorical
gross
speed.
Here are the tests:
///////IPERF2/////// Tests are quite good scoring 88% of the
bottleneck.
Note: iperf2 can use only 1 connection from a bond.(it's a well
know issue).
[ ID] Interval Transfer Bandwidth
[ 12] 0.0-10.0 sec 9.55 GBytes 8.21 Gbits/sec
[ 3] 0.0-10.0 sec 10.3 GBytes 8.81 Gbits/sec
[ 5] 0.0-10.0 sec 9.54 GBytes 8.19 Gbits/sec
[ 7] 0.0-10.0 sec 9.52 GBytes 8.18 Gbits/sec
[ 6] 0.0-10.0 sec 9.96 GBytes 8.56 Gbits/sec
[ 8] 0.0-10.0 sec 12.1 GBytes 10.4 Gbits/sec
[ 9] 0.0-10.0 sec 12.3 GBytes 10.6 Gbits/sec
[ 10] 0.0-10.0 sec 10.2 GBytes 8.80 Gbits/sec
[ 11] 0.0-10.0 sec 9.34 GBytes 8.02 Gbits/sec
[ 4] 0.0-10.0 sec 10.3 GBytes 8.82 Gbits/sec
[SUM] 0.0-10.0 sec 103 GBytes 88.6 Gbits/sec
///////RADOS BENCH
Take in consideration the maximum hypotetical speed of 48Gbit/s
tests
(due to disks bottleneck), tests are not good enought.
* Average MB/s in write is almost 5-7Gbit/sec (12,5% of the
mhs)
* Average MB/s in seq read is almost 24Gbit/sec (50% of the
mhs)
* Average MB/s in random read is almost 27Gbit/se (56,25% of
the mhs).
Here are the reports.
Write:
# rados bench -p scbench 10 write --no-cleanup
Total time run: 10.229369
Total writes made: 1538
Write size: 4194304
Object size: 4194304
Bandwidth (MB/sec): 601.406
Stddev Bandwidth: 357.012
Max bandwidth (MB/sec): 1080
Min bandwidth (MB/sec): 204
Average IOPS: 150
Stddev IOPS: 89
Max IOPS: 270
Min IOPS: 51
Average Latency(s): 0.106218
Stddev Latency(s): 0.198735
Max latency(s): 1.87401
Min latency(s): 0.0225438
sequential read:
# rados bench -p scbench 10 seq
Total time run: 2.054359
Total reads made: 1538
Read size: 4194304
Object size: 4194304
Bandwidth (MB/sec): 2994.61
Average IOPS 748
Stddev IOPS: 67
Max IOPS: 802
Min IOPS: 707
Average Latency(s): 0.0202177
Max latency(s): 0.223319
Min latency(s): 0.00589238
random read:
# rados bench -p scbench 10 rand
Total time run: 10.036816
Total reads made: 8375
Read size: 4194304
Object size: 4194304
Bandwidth (MB/sec): 3337.71
Average IOPS: 834
Stddev IOPS: 78
Max IOPS: 927
Min IOPS: 741
Average Latency(s): 0.0182707
Max latency(s): 0.257397
Min latency(s): 0.00469212
//------------------------------------
It's seems like that there are some bottleneck somewhere that we
are
understimating.
Can you help me to found it?
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