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

Maged Mokhtar mmokhtar at petasan.org
Tue Nov 13 23:36:00 PST 2018


Hi Dave,

The SSD journal will help boost iops  & latency which will be more 
apparent for small block sizes. The rados benchmark default block size 
is 4M, use the -b option to specify the size. Try at 4k, 32k, 64k ...
As a side note, this is a rados level test, the rbd image size is not 
relevant here.

Maged.

On 14/11/18 06:21, Dave.Chen at Dell.com 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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> ceph-users at lists.ceph.com
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