On 08/24/2012 06:41 PM, Denis Fondras wrote:
In my opinions, performances from RBD client are decent.
Unfortunately I need concurrent access and CephFS is really appealing in
that respect.
Ouch, that's taking a while! In addition to the comments that David
made, be aware that you are also testing the metadata server with
cephFS. Right now that's not getting a lot of attention as we are
primarily focusing on RADOS performance at the moment. For this kind of
test though, distributed filesystems will never be as good as local
disks...
Yes, it may be the MDS that is the bottleneck. Perhaps I should have a
lot of them...
Multi-MDS isn't working that great yet. In fact, CephFS hasn't gotten
that much attention lately.
Most of the work went into RADOS and RBD. In the next iterations the
focus will go to CephFS again, but right now it's not that well maintained.
Are you putting both journals on the SSD when you add an OSD? If so,
what's the throughput your SSD can sustain?
Both journals are on the SSD. It seems that when I do "ceph-osd -i $id
--mkfs --mkkey" it creates the journal according to the settings in
ceph.conf.
I did some tests and my SSD drive is somewhat broken... Crucial C300 is
a bit old and can only do 80MB/s writing.
You may want to check and see how big the IOs going to disk are on the
OSD node, and how quickly you are filling up the journal vs writing out
to disk. "collectl -sD -oT" will give you a nice report. Iostat can
probably tell you all of the same stuff with the right flags.
Thank you for that tool.
Denis
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