On Tue, Oct 1, 2019 at 7:54 AM Robert LeBlanc <robert@xxxxxxxxxxxxx> wrote:
>
> On Mon, Sep 30, 2019 at 5:12 PM Sasha Litvak
> <alexander.v.litvak@xxxxxxxxx> wrote:
> >
> > At this point, I ran out of ideas. I changed nr_requests and readahead parameters to 128->1024 and 128->4096, tuned nodes to performance-throughput. However, I still get high latency during benchmark testing. I attempted to disable cache on ssd
> >
> > for i in {a..f}; do hdparm -W 0 -A 0 /dev/sd$i; done
> >
> > and I think it make things not better at all. I have H740 and H730 controllers with drives in HBA mode.
> >
> > Other them converting them one by one to RAID0 I am not sure what else I can try.
> >
> > Any suggestions?
>
> If you haven't already tried this, add this to your ceph.conf and
> restart your OSDs, this should help bring down the variance in latency
> (It will be the default in Octopus):
>
> osd op queue = wpq
> osd op queue cut off = high
I should clarify. This will reduce the variance in latency for client
OPs. If this counter is also including recovery/backfill/deep_scrub
OP-, then the latency can still be high as these settings make
recovery/backfill/deep_scrub less impactful to client I/O at the cost
of them possibly being delayed a bit.
----------------
Robert LeBlanc
PGP Fingerprint 79A2 9CA4 6CC4 45DD A904 C70E E654 3BB2 FA62 B9F1
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