Re: Benchmark performance when using SSD as the journal

<Dave.Chen@xxxxxxxx> · Wed, 14 Nov 2018 04:45:26 +0000

Thanks Merrick!

I checked with Intel spec [1], the performance Intel said is,

·  Sequential Read (up to) 500 MB/s

·  Sequential Write (up to) 330 MB/s

·  Random Read (100% Span) 72000 IOPS

·  Random Write (100% Span) 20000 IOPS

I think these indicator should be must better than general HDD, and I have run read/write commands with “rados bench” respectively,   there should be some difference.

And is there any kinds of configuration that could give us any performance gain with this SSD (Intel S4500)?

[1] 
https://ark.intel.com/products/120521/Intel-SSD-DC-S4500-Series-480GB-2-5in-SATA-6Gb-s-3D1-TLC-

Best Regards,
Dave Chen

From: Ashley Merrick <singapore@xxxxxxxxxxxxxx> 

Sent: Wednesday, November 14, 2018 12:30 PM

To: Chen2, Dave

Cc: ceph-users

Subject: Re: [ceph-users] Benchmark performance when using SSD as the journal

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Only certain SSD's are good for CEPH Journals as can be seen @ https://www.sebastien-han.fr/blog/2014/10/10/ceph-how-to-test-if-your-ssd-is-suitable-as-a-journal-device/

The SSD your using isn't listed but doing a quick search online it appears to be a SSD designed for read workloads as a "upgrade" from a HD so probably is not designed for the high write requirements a journal demands. 

Therefore when it's been hit by 3 OSD's of workloads your not going to get much more performance out of it than you would just using the disk as your seeing.

On Wed, Nov 14, 2018 at 12:21 PM <Dave.Chen@xxxxxxxx> wrote:

Hi all,

We want to compare the performance between HDD partition as the journal (inline from OSD disk) and SSD partition as the journal, here is what we have done, we have 3 nodes used
 as Ceph OSD,  each has 3 OSD on it. Firstly, we created the OSD with journal from OSD partition, and run “rados bench” utility to test the performance, and then migrate the journal from HDD to SSD (Intel S4500) and run “rados bench” again, the expected result
 is SSD partition should be much better than HDD, but the result shows us there is nearly no change,

The configuration of Ceph is as below,
pool size: 3
osd size: 3*3
pg (pgp) num: 300
osd nodes are separated across three different nodes
rbd image size: 10G (10240M)

The utility I used is,
rados bench -p rbd $duration write
rados bench -p rbd $duration seq
rados bench -p rbd $duration rand

Is there anything wrong from what I did?  Could anyone give me some suggestion?

Best Regards,
Dave Chen

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