Le 07/03/2014 10:50, Indra Pramana a écrit :
Hi,
I have a Ceph cluster, currently with 5 osd servers and around 22 OSDs
with SSD drives and I noted that the I/O speed, especially write
access to the cluster is degrading over time. When we first started
the cluster, we can get up to 250-300 MB/s write speed to the SSD
cluster but now we can only get up to half the mark. Furthermore, it
now fluctuates so sometimes I can get slightly better speed but on
another time I get very bad result.
We started with 3 osd servers and 12 OSDs and gradually add more
servers. We are using KVM hypervisors as the Ceph clients and
connection between clients and servers and between the servers are
through 10 GBps switch with jumbo frames enabled on all interfaces.
Any advice on how can I start to troubleshoot what might have caused
the degradation of the I/O speed? Does utilisation contributes to it
(since now we have more users compared to last time when we started)?
Any optimisation we can do to improve the I/O performance?
Appreciate any advice, thank you.
Cheers.
You should test the performance of one (each ?) OSD, directly on the OSD
server (with fio on /var/lib/ceph/osd/...)
If you see the same problem, perhaps you have a SSD which has no more
empty cells, and has to do many deletes.
You must trim it (fstrim if it's supported by your filesystem).
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