Well, preferring faster clock CPUs for SSD scenarios has been floated several times over the last few months on this list. And realistic or not, Nick's and Kostas' setup are similar enough (testing single disk) that it's a distinct possibility.
Anyway, as mentioned measuring the performance counters would probably provide more insight.
On Sun, Jun 25, 2017 at 4:53 AM, Willem Jan Withagen <wjw@xxxxxxxxxxx> wrote:
My understanding was this test is targeting latency more than IOPS. This is probably why its was run using QD=1. It also makes sense that cpu freq will be more important than cores.
But then it is not generic enough to be used as an advise!It is just a line in 3D-space.As there are so many--WjWOn 2017-06-24 12:52, Willem Jan Withagen wrote:
On 24-6-2017 05:30, Christian Wuerdig wrote:The general advice floating around is that your want CPUs with high
clock speeds rather than more cores to reduce latency and increase IOPS
for SSD setups (see also
http://www.sys-pro.co.uk/ceph-storage-fast-cpus-ssd- ) Soperformance/
something like a E5-2667V4 might bring better results in that situation.
Also there was some talk about disabling the processor C states in order
to bring latency down (something like this should be easy to test:
https://stackoverflow.com/a/22482722/220986 )
I would be very careful to call this a general advice...
Although the article is interesting, it is rather single sided.
The only thing is shows that there is a lineair relation between
clockspeed and write or read speeds???
The article is rather vague on how and what is actually tested.
By just running a single OSD with no replication a lot of the
functionality is left out of the equation.
Nobody is running just 1 osD on a box in a normal cluster host.
Not using a serious SSD is another source of noise on the conclusion.
More Queue depth can/will certainly have impact on concurrency.
I would call this an observation, and nothing more.
--WjW
On Sat, Jun 24, 2017 at 1:28 AM, Kostas Paraskevopoulos
<reverend.x3@xxxxxxxxx <mailto:reverend.x3@xxxxxxxxx>> wrote:
Hello,
We are in the process of evaluating the performance of a testing
cluster (3 nodes) with ceph jewel. Our setup consists of:
3 monitors (VMs)
2 physical servers each connected with 1 JBOD running Ubuntu Server
16.04
Each server has 32 threads @2.1GHz and 128GB RAM.
The disk distribution per server is:
38 * HUS726020ALS210 (SAS rotational)
2 * HUSMH8010BSS200 (SAS SSD for journals)
2 * ST1920FM0043 (SAS SSD for data)
1 * INTEL SSDPEDME012T4 (NVME measured with fio ~300K iops)
Since we don't currently have a 10Gbit switch, we test the performance
with the cluster in a degraded state, the noout flag set and we mount
rbd images on the powered on osd node. We confirmed that the network
is not saturated during the tests.
We ran tests on the NVME disk and the pool created on this disk where
we hoped to get the most performance without getting limited by the
hardware specs since we have more disks than CPU threads.
The nvme disk was at first partitioned with one partition and the
journal on the same disk. The performance on random 4K reads was
topped at 50K iops. We then removed the osd and partitioned with 4
data partitions and 4 journals on the same disk. The performance
didn't increase significantly. Also, since we run read tests, the
journals shouldn't cause performance issues.
We then ran 4 fio processes in parallel on the same rbd mounted image
and the total iops reached 100K. More parallel fio processes didn't
increase the measured iops.
Our ceph.conf is pretty basic (debug is set to 0/0 for everything) and
the crushmap just defines the different buckets/rules for the disk
separation (rotational, ssd, nvme) in order to create the required
pools
Is the performance of 100.000 iops for random 4K read normal for a
disk that on the same benchmark runs at more than 300K iops on the
same hardware or are we missing something?
Best regards,
Kostas
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