In a long term use I also had some issues with flashcache and enhanceio. I've noticed frequent slow requests.
Andrei ----- Original Message ----- > From: "Robert LeBlanc" <rob...@leblancnet.us> > To: "Nick Fisk" <n...@fisk.me.uk> > Cc: ceph-users@lists.ceph.com > Sent: Friday, 20 March, 2015 8:14:16 PM > Subject: Re: [ceph-users] OSD + Flashcache + udev + Partition uuid > We tested bcache and abandoned it for two reasons. > 1. Didn't give us any better performance than journals on SSD. > 2. We had lots of corruption of the OSDs and were rebuilding them > frequently. > Since removing them, the OSDs have been much more stable. > On Fri, Mar 20, 2015 at 4:03 AM, Nick Fisk < n...@fisk.me.uk > wrote: > > > -----Original Message----- > > > > From: ceph-users [mailto: ceph-users-boun...@lists.ceph.com ] On > > > Behalf Of > > > > Burkhard Linke > > > > Sent: 20 March 2015 09:09 > > > > To: ceph-users@lists.ceph.com > > > > Subject: Re: [ceph-users] OSD + Flashcache + udev + Partition > > > uuid > > > > > > > > Hi, > > > > > > > > On 03/19/2015 10:41 PM, Nick Fisk wrote: > > > > > I'm looking at trialling OSD's with a small flashcache device > > > > over > > > > > them to hopefully reduce the impact of metadata updates when > > > > doing > > > > small block io. > > > > > Inspiration from here:- > > > > > > > > > > http://comments.gmane.org/gmane.comp.file-systems.ceph.devel/12083 > > > > > > > > > > One thing I suspect will happen, is that when the OSD node > > > > starts > > > > up > > > > > udev could possibly mount the base OSD partition instead of > > > > > flashcached device, as the base disk will have the ceph > > > > partition > > > > uuid > > > > > type. This could result in quite nasty corruption. > > > > I ran into this problem with an enhanceio based cache for one of > > > our > > > > database servers. > > > > > > > > I think you can prevent this problem by using bcache, which is > > > also > > > integrated > > > > into the official kernel tree. It does not act as a drop in > > > replacement, > > > but > > > > creates a new device that is only available if the cache is > > > initialized > > > correctly. A > > > > GPT partion table on the bcache device should be enough to allow > > > the > > > > standard udev rules to kick in. > > > > > > > > I haven't used bcache in this scenario yet, and I cannot comment > > > on > > > its > > > speed > > > > and reliability compared to other solutions. But from the > > > operational > > > point of > > > > view it is "safer" than enhanceio/flashcache. > > > I did look at bcache, but there are a lot of worrying messages on > > the > > > mailing list about hangs and panics that has discouraged me > > slightly > > from > > > it. I do think it is probably the best solution, but I'm not > > convinced about > > > the stability. > > > > > > > > Best regards, > > > > Burkhard > > > > _______________________________________________ > > > > 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 > > _______________________________________________ > ceph-users mailing list > ceph-users@lists.ceph.com > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
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