AFAIK the snapshots are useful when the journal sits inside the OSD filesystem. In case the journal is on a separate filesystem/device then OSD BTRFS snapshots can be safely disabled. I have done so on my OSDs as they all use external journals and experienced a reduction in periodic writes, but they are not completely gone.
pon., 22.06.2015 o 11:27 użytkownik Jan Schermer <j...@schermer.cz> napisał: > I don’t run Ceph on btrfs, but isn’t this related to the btrfs > snapshotting feature ceph uses to ensure a consistent journal? > > Jan > > On 19 Jun 2015, at 14:26, Lionel Bouton <lionel+c...@bouton.name> wrote: > > On 06/19/15 13:42, Burkhard Linke wrote: > > > Forget the reply to the list... > > -------- Forwarded Message -------- Subject: Re: [ceph-users] Unexpected > disk write activity with btrfs OSDs Date: Fri, 19 Jun 2015 09:06:33 +0200 > From: > Burkhard Linke <burkhard.li...@computational.bio.uni-giessen.de> > <burkhard.li...@computational.bio.uni-giessen.de> To: Lionel Bouton > <lionel+c...@bouton.name> <lionel+c...@bouton.name> > > Hi, > > On 06/18/2015 11:28 PM, Lionel Bouton wrote: > > Hi, > *snipsnap* > > > - Disks with btrfs OSD have a spike of activity every 30s (2 intervals > > of 10s with nearly 0 activity, one interval with a total amount of > > writes of ~120MB). The averages are : 4MB/s, 100 IO/s. > > Just a guess: > > btrfs has a commit interval which defaults to 30 seconds. > > You can verify this by changing the interval with the commit=XYZ mount > option. > > > I know and I tested commit intervals of 60 and 120 seconds without any > change. As this is directly linked to filestore max sync interval I didn't > report this test result. > > Best regards, > > Lionel > _______________________________________________ > ceph-users mailing list > ceph-users@lists.ceph.com > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com > > > _______________________________________________ > ceph-users mailing list > ceph-users@lists.ceph.com > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com >
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