Hi Guys,
We ran tests a while back looking at different IO elevators but they are
quite old now:
http://ceph.com/community/ceph-bobtail-performance-io-scheduler-comparison/
On 04/05/2015 08:36 PM, Francois Lafont wrote:
On 04/06/2015 02:54, Lionel Bouton wrote:
I have never tested these parameters (osd_disk_thread_ioprio_priority and
osd_disk_thread_ioprio_class), but did you check that the I/O scheduler of
the disks is cfq?
Yes I did.
Ah ok. It was just in case. :)
Because, if I understand well, these parameters have no
effect if the I/O scheduler is no cfq
AFAIK cfq is the only elevator supporting priorities in the mainline kernel.
Ok.
By the way, even if I don't use these parameters, should I use cfq I/O
scheduler instead of deadline? Is there a best I/O scheduler for Ceph?
It probably depends on your actual workload. It may depend on your
hardware too: some benchmarks have shown it to perform faster on HDD but
slower than deadline or noop on SSD.
Interesting...
I have only HDD (no SSD) and currently the I/O scheduler is "deadline"
(the default scheduler of my Ubuntu Trusty). So, I'll think about
switching from "deadline" to "cfq"...
Thanks for your answer Lionel. ;)
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