Re: mon IO usage

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On Tue, 21 May 2013, Sylvain Munaut wrote:
> Hi,
> 
> >> So, AFAICT, the bulk of the write would be writing out the pgmap to
> >> disk every second or so.
> >
> > It should be writing out the full map only every N commits... see 'paxos
> > stash full interval', which defaults to 25.
> 
> But doesn't it also write it in full when there is a new pgmap ?
> 
> I have a new one about every second and its size * period seemed to
> match the IO rate pretty well which it why I thought it was the reason
> for the IO.

Hmm.  Can you generate a log with 'debug mon = 20', 'debug paxos = 20', 
'debug ms = 1' for a few minutes over which you see a high data rate and 
send it my way?  It sounds like there is something wrong with the 
stash_full logic.

Thanks!

> >> Is it really needed to write it in full ? It doesn't change all that
> >> much AFAICT, so writing incremental changes with only periodic flush
> >> might be a better option ?
> >
> > Right.  It works this way now only because we haven't fully transitioned
> > from the old scheme.  The next step is to store the PGMap over lots of
> > leveldb keys (one per pg) so that there is no big encode/decode of the
> > entire PGMap structure...
> 
> Makes sense. I'm not sure of the "per-key" overhead of leveldb though,
> in case where there are lots ( > 10k ) PGs.

Yeah, it will be larger on-disk, but the io rate will at least be 
proportional to the update rate.  :)

sage
_______________________________________________
ceph-users mailing list
ceph-users@xxxxxxxxxxxxxx
http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com




[Index of Archives]     [Information on CEPH]     [Linux Filesystem Development]     [Ceph Development]     [Ceph Large]     [Ceph Dev]     [Linux USB Development]     [Video for Linux]     [Linux Audio Users]     [Yosemite News]     [Linux Kernel]     [Linux SCSI]     [xfs]


  Powered by Linux