On 5/6/14 08:07 , Xabier Elkano wrote:
Hi,
I'm designing a new ceph pool with new hardware and I would like to
1- With journal in SSDs
2- With journal in a partition in the spinners.
I don't have enough experience to give advice, so I'll tell my story.
I'm using RGW, and my only performance concern is latency on the human
scale. I setup a cluster with the journal on the spinning disks, and
everything was great. Read performance was great, and write performance
was acceptable.
Then came the day that I wanted to expand the cluster. As soon as the
cluster went to remapped+backfill, performance went downhill. Reads
would take several seconds, and writes would take long enough that the
HTTP load balancer would kick those nodes out.
It was my own fault. I had neglected to adjust the osd parameters
related to backfilling. I finally got things under control with:
[osd]
osd max backfills = 1
osd recovery op priority = 1
Things are working, but there is a human noticeable performance drop
when backfilling. Because of the low max backfills, it takes a long
time to add new OSDs. The most recent OSD addition is still backfilling
after 4 days and 2.5 TiB. Users are grumbling about the performance,
but nobody is yelling at me.
I'm in the middle of adding some new nodes with SSD journals. Once that
finishes, I'm going to replace the existing nodes' OS disks with some
Intel SC3700 SSDs, and move the journals to those.
--
*Craig Lewis*
Senior Systems Engineer
Office +1.714.602.1309
Email cle...@centraldesktop.com <mailto:cle...@centraldesktop.com>
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