100GB objects (or ~40 on a hard drive!) are way too large for you to get an effective random distribution. -Greg
On Thu, Jan 8, 2015 at 5:25 PM, Mark Nelson <mark.nel...@inktank.com> wrote: > On 01/08/2015 03:35 PM, Michael J Brewer wrote: >> >> Hi all, >> >> I'm working on filling a cluster to near capacity for testing purposes. >> Though I'm noticing that it isn't storing the data uniformly between >> OSDs during the filling process. I currently have the following levels: >> >> Node 1: >> /dev/sdb1 3904027124 2884673100 1019354024 74% >> /var/lib/ceph/osd/ceph-0 >> /dev/sdc1 3904027124 2306909388 1597117736 60% >> /var/lib/ceph/osd/ceph-1 >> /dev/sdd1 3904027124 3296767276 607259848 85% >> /var/lib/ceph/osd/ceph-2 >> /dev/sde1 3904027124 3670063612 233963512 95% >> /var/lib/ceph/osd/ceph-3 >> >> Node 2: >> /dev/sdb1 3904027124 3250627172 653399952 84% >> /var/lib/ceph/osd/ceph-4 >> /dev/sdc1 3904027124 3611337492 292689632 93% >> /var/lib/ceph/osd/ceph-5 >> /dev/sdd1 3904027124 2831199600 1072827524 73% >> /var/lib/ceph/osd/ceph-6 >> /dev/sde1 3904027124 2466292856 1437734268 64% >> /var/lib/ceph/osd/ceph-7 >> >> I am using "rados put" to upload 100g files to the cluster, doing two at >> a time from two different locations. Is this expected behavior, or can >> someone shed light on why it is doing this? We're using the opensource >> version 80.7. We're also using the default CRUSH configuration. > > > So crush utilizes pseudo-random distributions, but sadly random > distributions tend to be clumpy and not perfectly uniform until you get to > very high sample counts. The gist of it is that if you have a really low > density of PGs/OSD and/or are very unlucky, you can end up with a skewed > distribution. If you are even more unlucky, you could compound that with a > streak of objects landing on PGs associated with some specific OSD. This > particular case looks rather bad. How many PGs and OSDs do you have? > >> >> Regards, >> *MICHAEL J. BREWER* >> ------------------------------------------------------------------------ >> *Phone:* 1-512-286-5596 | *Tie-Line:* 363-5596* >> E-mail:*_mjbre...@us.ibm.com_ <mailto:mjbre...@us.ibm.com> >> >> >> 11501 Burnet Rd >> Austin, TX 78758-3400 >> United States >> >> >> >> >> _______________________________________________ >> 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
