Re: Benchmark performance when using SSD as the journal

[Ashley Merrick <singapore@xxxxxxxxxxxxxx>]

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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