On Sat, 15 Apr 2017, Aaron Ten Clay wrote: > Hi all, > > Our cluster is experiencing a very odd issue and I'm hoping for some > guidance on troubleshooting steps and/or suggestions to mitigate the issue. > tl;dr: Individual ceph-osd processes try to allocate > 90GiB of RAM and are > eventually nuked by oom_killer. My guess is that there there is a bug in a decoding path and it's trying to allocate some huge amount of memory. Can you try setting a memory ulimit to something like 40gb and then enabling core dumps so you can get a core? Something like ulimit -c unlimited ulimit -m 20000000 or whatever the corresponding systemd unit file options are... Once we have a core file it will hopefully be clear who is doing the bad allocation... sage > > I'll try to explain the situation in detail: > > We have 24-4TB bluestore HDD OSDs, and 4-600GB SSD OSDs. The SSD OSDs are in > a different CRUSH "root", used as a cache tier for the main storage pools, > which are erasure coded and used for cephfs. The OSDs are spread across two > identical machines with 128GiB of RAM each, and there are three monitor > nodes on different hardware. > > Several times we've encountered crippling bugs with previous Ceph releases > when we were on RC or betas, or using non-recommended configurations, so in > January we abandoned all previous Ceph usage, deployed LTS Ubuntu 16.04, and > went with stable Kraken 11.2.0 with the configuration mentioned above. > Everything was fine until the end of March, when one day we find all but a > couple of OSDs are "down" inexplicably. Investigation reveals oom_killer > came along and nuked almost all the ceph-osd processes. > > We've gone through a bunch of iterations of restarting the OSDs, trying to > bring them up one at a time gradually, all at once, various configuration > settings to reduce cache size as suggested in this ticket: > http://tracker.ceph.com/issues/18924... > > I don't know if that ticket really pertains to our situation or not, I have > no experience with memory allocation debugging. I'd be willing to try if > someone can point me to a guide or walk me through the process. > > I've even tried, just to see if the situation was transitory, adding over > 300GiB of swap to both OSD machines. The OSD procs managed to allocate, in a > matter of 5-10 minutes, more than 300GiB of RAM pressure and became > oom_killer victims once again. > > No software or hardware changes took place around the time this problem > started, and no significant data changes occurred either. We added about > 40GiB of ~1GiB files a week or so before the problem started and that's the > last time data was written. > > I can only assume we've found another crippling bug of some kind, this level > of memory usage is entirely unprecedented. What can we do? > > Thanks in advance for any suggestions. > -Aaron > >
