To answer my own question it seems that you can change settings on the fly using
ceph tell osd.* injectargs '--osd_tier_promote_max_bytes_sec 5242880' osd.0: osd_tier_promote_max_bytes_sec = '5242880' (unchangeable) However the response seems to imply I can't change this setting. Is there an other way to change these settings? On Sun, May 8, 2016 at 2:37 PM, Peter Kerdisle <peter.kerdi...@gmail.com> wrote: > Hey guys, > > I noticed the merge request that fixes the switch around here > https://github.com/ceph/ceph/pull/8912 > > I had two questions: > > > - Does this effect my performance in any way? Could it explain the > slow requests I keep having? > - Can I modify these settings manually myself on my cluster? > > Thanks, > > Peter > > > On Fri, May 6, 2016 at 9:58 AM, Peter Kerdisle <peter.kerdi...@gmail.com> > wrote: > >> Hey Mark, >> >> Sorry I missed your message as I'm only subscribed to daily digests. >> >> >>> Date: Tue, 3 May 2016 09:05:02 -0500 >>> From: Mark Nelson <mnel...@redhat.com> >>> To: ceph-users@lists.ceph.com >>> Subject: Re: [ceph-users] Erasure pool performance expectations >>> Message-ID: <df3de049-a7f9-7f86-3ed3-47079e401...@redhat.com> >>> Content-Type: text/plain; charset=windows-1252; format=flowed >>> In addition to what nick said, it's really valuable to watch your cache >>> tier write behavior during heavy IO. One thing I noticed is you said >>> you have 2 SSDs for journals and 7 SSDs for data. >> >> >> I thought the hardware recommendations were 1 journal disk per 3 or 4 >> data disks but I think I might have misunderstood it. Looking at my journal >> read/writes they seem to be ok though: >> https://www.dropbox.com/s/er7bei4idd56g4d/Screenshot%202016-05-06%2009.55.30.png?dl=0 >> >> However I started running into a lot of slow requests (made a separate >> thread for those: Diagnosing slow requests) and now I'm hoping these >> could be related to my journaling setup. >> >> >>> If they are all of >>> the same type, you're likely bottlenecked by the journal SSDs for >>> writes, which compounded with the heavy promotions is going to really >>> hold you back. >>> What you really want: >>> 1) (assuming filestore) equal large write throughput between the >>> journals and data disks. >> >> How would one achieve that? >> >>> >>> 2) promotions to be limited by some reasonable fraction of the cache >>> tier and/or network throughput (say 70%). This is why the >>> user-configurable promotion throttles were added in jewel. >> >> Are these already in the docs somewhere? >> >>> >>> 3) The cache tier to fill up quickly when empty but change slowly once >>> it's full (ie limiting promotions and evictions). No real way to do >>> this yet. >>> Mark >> >> >> Thanks for your thoughts. >> >> Peter >> >> >
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