> -----Original Message-----
> From: Jacek Jarosiewicz [mailto:jjarosiew...@supermedia.pl]
> Sent: 19 August 2015 14:28
> To: Nick Fisk <n...@fisk.me.uk>; ceph-us...@ceph.com
> Subject: Re: [ceph-users] requests are blocked - problem
>
> On 08/19/2015 10:58 AM, Nick Fisk wrote:
> >> -----Original Message-----
> >> From: ceph-users [mailto:ceph-users-boun...@lists.ceph.com] On Behalf
> >> Of Jacek Jarosiewicz
> >> Sent: 19 August 2015 09:29
> >> To: ceph-us...@ceph.com
> >> Subject: [ceph-users] requests are blocked - problem
> >
> > I would suggest running the fio tests again, just to make sure that there
> isn't a problem with your newer config, but I suspect you will see equally bad
> performance with the fio tests now that the cache tier has begun to be more
> populated.
> >
>
> Ok, I did the tests and You're right - the full cache was the problem.
> After flushing cache and running fio results are again good (fast).
>
> Is there a way to tune the cache parameters so that the whole cluster
> doesn't slow down that much and doesn't block requests?
>
> We use defaults for the cache pool from the documentation:
> hit_set_period 3600
> cache_min_flush_age 600
> cache_min_evict_age 1800
>
Although you may get some benefit from tweaking parameters, I suspect you are
nearer the performance ceiling for the current implementation of the tiering
code. Could you post all the variables you set for the tiering including
target_max_bytes and the dirty/full ratios.
Since you are doing maildirs, which will have lots of small files, you might
also want to try making the object size of the RBD smaller. This will mean less
data is needed to be shifted on each promotion/flush.
> J
>
> --
> Jacek Jarosiewicz
> Administrator Systemów Informatycznych
>
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