On Sat, Dec 5, 2020 at 2:41 PM Janek Bevendorff <janek.bevendorff@xxxxxxxxxxxxx> wrote: > > On 05/12/2020 09:26, Dan van der Ster wrote: > > Hi Janek, > > > > I'd love to hear your standard maintenance procedures. Are you > > cleaning up those open files outside of "rejoin" OOMs ? > > No, of course not. But those rejoin problems happen more often than I'd > like them to. It has become much better with recent releases, OK sounds good. We very rarely restart MDSs, and only recently upgraded to nautilus (from L) so haven't yet had many opportunities to see how often we'll suffer this rejoin issue on our most active cluster. (Only one of our test clusters saw this happen so far, during mimic days, and this provoked us to move all MDSs to 64GB VMs, with mds cache mem limit = 4GB, so there is a large amount of RAM available in case it's needed. BTW the PR introduces a new option `mds_oft_prefetch_dirfrags`; it remains to be seen exactly how true/false impacts memory consumption. > but if one of the clients trains a Tensorflow model from files in the CephFS or > when our Hadoop cluster starts reading from it, the MDS will almost > certainly crash or at least degrade massively in performance. S3 doesn't > have these problems at all, obviously. What do the crashes look like with the TF training? Do you have a tracker? How many client sessions do need to crash an MDS? > That said, our metadata pool resides on rotating platters at the moment > and we plan to move it to SSDs, but that should only fix latency issues > and not the crash and rejoin problems (btw it doesn't matter how long > you set the heartbeat interval, the rejoining MDS will always be > replaced by a standby before it's finished). It works afaict. We needed mds beacon grace = several thousand seconds to survive a 30 minute MDS outage, without any failover to standby. This happened during our L->N upgrade, due to some MDS export extreme slowness. Cheers, Dan P.S. I've seen an older thread of yours about tuning caps recall. I've recently done some testing there and will reply with my input. -- Dan > > > > > I guess we're pretty lucky with our CephFS's because we have more than > > 1k clients and it is pretty solid (though the last upgrade had a > > hiccup decreasing down to single active MDS). > > > > -- Dan > > > > > > > > On Fri, Dec 4, 2020 at 8:20 PM Janek Bevendorff > > <janek.bevendorff@xxxxxxxxxxxxx> wrote: > >> This is very common issue. Deleting mdsX_openfiles.Y has become part of > >> my standard maintenance repertoire. As soon as you have a few more > >> clients and one of them starts opening and closing files in rapid > >> succession (or does other metadata-heavy things), it becomes very likely > >> that the MDS crashes and is unable to recover. > >> > >> There have been numerous fixes in the past, which improved the overall > >> stability, but it is far from perfect. I am happy to see another patch > >> in that direction, but I believe more effort needs to be spent here. It > >> is way too easy to DoS the MDS from a single client. Our 78-node CephFS > >> beats our old NFS RAID server in terms of throughput, but latency and > >> stability are way behind. > >> > >> Janek > >> > >> On 04/12/2020 11:39, Dan van der Ster wrote: > >>> Excellent! > >>> > >>> For the record, this PR is the plan to fix this: > >>> https://github.com/ceph/ceph/pull/36089 > >>> (nautilus, octopus PRs here: https://github.com/ceph/ceph/pull/37382 > >>> https://github.com/ceph/ceph/pull/37383) > >>> > >>> Cheers, Dan > >>> > >>> On Fri, Dec 4, 2020 at 11:35 AM Anton Aleksandrov <anton@xxxxxxxxxxxxxx> wrote: > >>>> Thank you very much! This solution helped: > >>>> > >>>> Stop all MDS, then: > >>>> # rados -p cephfs_metadata_pool rm mds0_openfiles.0 > >>>> then start one MDS. > >>>> > >>>> We are back online. Amazing!!! :) > >>>> > >>>> > >>>> On 04.12.2020 12:20, Dan van der Ster wrote: > >>>>> Please also make sure the mds_beacon_grace is high on the mon's too. > >>>>> > >>>>> it doesn't matter which mds you select to be the running one. > >>>>> > >>>>> Is the processing getting killed, restarted? > >>>>> If you're confident that the mds is getting OOM killed during rejoin > >>>>> step, then you might find this useful: > >>>>> http://lists.ceph.com/pipermail/ceph-users-ceph.com/2018-August/028964.html > >>>>> > >>>>> Stop all MDS, then: > >>>>> # rados -p cephfs_metadata_pool rm mds0_openfiles.0 > >>>>> then start one MDS. > >>>>> > >>>>> -- Dan > >>>>> > >>>>> On Fri, Dec 4, 2020 at 11:05 AM Anton Aleksandrov <anton@xxxxxxxxxxxxxx> wrote: > >>>>>> Yes, MDS eats all memory+swap, stays like this for a moment and then > >>>>>> frees memory. > >>>>>> > >>>>>> mds_beacon_grace was already set to 1800 > >>>>>> > >>>>>> Also on other it is seen this message: Map has assigned me to become a > >>>>>> standby. > >>>>>> > >>>>>> Does it matter, which MDS we stop and which we leave running? > >>>>>> > >>>>>> Anton > >>>>>> > >>>>>> > >>>>>> On 04.12.2020 11:53, Dan van der Ster wrote: > >>>>>>> How many active MDS's did you have? (max_mds == 1, right?) > >>>>>>> > >>>>>>> Stop the other two MDS's so you can focus on getting exactly one running. > >>>>>>> Tail the log file and see what it is reporting. > >>>>>>> Increase mds_beacon_grace to 600 so that the mon doesn't fail this MDS > >>>>>>> while it is rejoining. > >>>>>>> > >>>>>>> Is that single MDS running out of memory during the rejoin phase? > >>>>>>> > >>>>>>> -- dan > >>>>>>> > >>>>>>> On Fri, Dec 4, 2020 at 10:49 AM Anton Aleksandrov <anton@xxxxxxxxxxxxxx> wrote: > >>>>>>>> Hello community, > >>>>>>>> > >>>>>>>> we are on ceph 13.2.8 - today something happenned with one MDS and cephs > >>>>>>>> status tells, that filesystem is degraded. It won't mount either. I have > >>>>>>>> take server with MDS, that was not working down. There are 2 more MDS > >>>>>>>> servers, but they stay in "rejoin" state. Also only 1 is shown in > >>>>>>>> "services", even though there are 2. > >>>>>>>> > >>>>>>>> Both running MDS servers have these lines in their logs: > >>>>>>>> > >>>>>>>> heartbeat_map is_healthy 'MDSRank' had timed out after 15 > >>>>>>>> mds.beacon.mds2 Skipping beacon heartbeat to monitors (last acked > >>>>>>>> 28.8979s ago); MDS internal heartbeat is not healthy! > >>>>>>>> > >>>>>>>> On one of MDS nodes I enabled more detailed debug, so I am getting there > >>>>>>>> also: > >>>>>>>> > >>>>>>>> mds.beacon.mds3 Sending beacon up:standby seq 178 > >>>>>>>> mds.beacon.mds3 received beacon reply up:standby seq 178 rtt 0.000999968 > >>>>>>>> > >>>>>>>> Makes no sense and too much stress in my head... Anyone could help please? > >>>>>>>> > >>>>>>>> Anton. > >>>>>>>> _______________________________________________ > >>>>>>>> ceph-users mailing list -- ceph-users@xxxxxxx > >>>>>>>> To unsubscribe send an email to ceph-users-leave@xxxxxxx > >>> _______________________________________________ > >>> ceph-users mailing list -- ceph-users@xxxxxxx > >>> To unsubscribe send an email to ceph-users-leave@xxxxxxx _______________________________________________ ceph-users mailing list -- ceph-users@xxxxxxx To unsubscribe send an email to ceph-users-leave@xxxxxxx
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