On 10/06/2015 10:14 AM, MailingLists - EWS wrote:
I have encountered a rather interesting issue with Ubuntu 14.04 LTS
running 3.19.0-30 kernel (Vivid) using Ceph Hammer (0.94.3).
With everything else identical in our testing cluster, no other changes
other than the kernel (apt-get install linux-image-generic-lts-vivid and
then a reboot), we are seeing a substantial drop in read performance as
indicated with rados bench.
Kernel 3.13.0.-65 (latest for Trusty): Read performance: 575MB/s
Kernel 3.19.0-30 (Vivid): Read performance: 175MB/s
Has anyone experienced this sort of performance drop?
Hi,
Very interesting! Did you upgrade the kernel on both the OSDs and
clients or just some of them? I remember there were some kernel
performance regressions a little while back. You might try running perf
during your tests and look for differences. Also, iperf might be worth
trying to see if it's a network regression.
I also have a script that compares output from sysctl which might be
worth trying to see if any defaults changes.
https://github.com/ceph/cbt/blob/master/tools/compare_sysctl.py
basically just save systctl -a with both kernels and pass them as
arguments to the python script.
Mark
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