Do you have anything particular in mind? I'm using mdb backend with maxsize = 1GB but currently the files are only about 23MB.
> > I am having quite a few openldap servers (slaves) running also, make > sure to use proper caching that saves a lot of disk io. > > > > > -----Original Message----- > Sent: 28 February 2019 13:56 > To: uwe.sauter...@gmail.com; Uwe Sauter; Ceph Users > Subject: *****SPAM***** Re: [ceph-users] Fwd: Re: Blocked ops after > change from filestore on HDD to bluestore on SDD > > "Advanced power loss protection" is in fact a performance feature, not a > safety one. > > > 28 февраля 2019 г. 13:03:51 GMT+03:00, Uwe Sauter > <uwe.sauter...@gmail.com> пишет: > > Hi all, > > thanks for your insights. > > Eneko, > > > We tried to use a Samsung 840 Pro SSD as OSD some time ago and > it was a no-go; it wasn't that performance was bad, it > just didn't work for the kind of use of OSD. Any HDD was > better than it (the disk was healthy and have been used in a > software raid-1 for a pair of years). > > I suggest you check first that your Samsung 860 Pro disks work > well for Ceph. Also, how is your host's RAM? > > > As already mentioned the hosts each have 64GB RAM. Each host has 3 > SSDs for OSD usage. Each OSD is using about 1.3GB virtual > memory / 400MB residual memory. > > > > Joachim, > > > I can only recommend the use of enterprise SSDs. We've tested > many consumer SSDs in the past, including your SSDs. Many > of them are not suitable for long-term use and some weard out > within 6 months. > > > Unfortunately I couldn't afford enterprise grade SSDs. But I > suspect that my workload (about 20 VMs for our infrastructure, the > most IO demanding is probably LDAP) is light enough that wearout > won't be a problem. > > The issue I'm seeing then is probably related to direct IO if using > bluestore. But with filestore, the file system cache probably > hides the latency issues. > > > Igor, > > > AFAIR Samsung 860 Pro isn't for enterprise market, you > shouldn't use consumer SSDs for Ceph. > > I had some experience with Samsung 960 Pro a while ago and it > turned out that it handled fsync-ed writes very slowly > (comparing to the original/advertised performance). Which one > can probably explain by the lack of power loss protection > for these drives. I suppose it's the same in your case. > > Here are a couple links on the topic: > > > https://www.percona.com/blog/2018/02/08/fsync-performance-storage-devices/ > > > https://www.sebastien-han.fr/blog/2014/10/10/ceph-how-to-test-if-your-ssd-is-suitable-as-a-journal-device/ > > > Power loss protection wasn't a criteria for me as the cluster hosts > are distributed in two buildings with separate battery backed > UPSs. As mentioned above I suspect the main difference for my case > between filestore and bluestore is file system cache vs. direct > IO. Which means I will keep using filestore. > > Regards, > > Uwe > ________________________________ > > ceph-users mailing list > ceph-users@lists.ceph.com > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com > > > -- > With best regards, > Vitaliy Filippov > > _______________________________________________ ceph-users mailing list ceph-users@lists.ceph.com http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
