On Wed, Jul 24, 2019 at 3:13 PM Janek Bevendorff < janek.bevendo...@uni-weimar.de> wrote:
> > which version? > > Nautilus, 14.2.2. > I mean kernel version > try mounting cephfs on a machine/vm with small memory (4G~8G), then rsync > your date into mount point of that machine. > > I could try running it in a memory-limited Docker container, but isn't > there a better way to achieve the same thing? This sounds like a bug to me. > A client having too much memory and failing to free its capabilities > shouldn't crash the server. If the server decides to drop things from its > cache, the client has to deal with it. > > Also in the long run, limiting the client's memory isn't a practical > solution. We are planning to use the CephFS from our compute cluster, whose > nodes have (and need) many more times the RAM that our storage servers have. > > > > >> >> >> >> The MDS nodes have Xeon E5-2620 v4 CPUs @2.10GHz with 32 threads (Dual >> CPU with 8 physical cores each) and 128GB RAM. CPU usage is rather mild. >> While MDSs are trying to rejoin, they tend to saturate a single thread >> shortly, but nothing spectacular. During normal operation, none of the >> cores is particularly under load. >> >> > While migrating to a Nautilus cluster recently, we had up to 14 >> > million inodes open, and we increased the cache limit to 16GiB. Other >> > than warnings about oversized cache, this caused no issues. >> >> I tried settings of 1, 2, 5, 6, 10, 20, 50, and 90GB. Other than getting >> rid of the cache size warnings (and sometimes allowing an MDS to rejoin >> without being kicked again after a few seconds), it did not change much >> in terms of the actual problem. Right now I can change it to whatever I >> want, it doesn't do anything, because rank 0 keeps being trashed anyway >> (the other ranks are fine, but the CephFS is down anyway). Is there >> anything useful I can give you to debug this? Otherwise I would try >> killing the MDS daemons so I can at least restore the CephFS to a >> semi-operational state. >> >> >> > >> > On Tue, Jul 23, 2019 at 2:30 PM Janek Bevendorff wrote: >> >> Hi, >> >> >> >> Disclaimer: I posted this before to the cheph.io mailing list, but >> from >> >> the answers I didn't get and a look at the archives, I concluded that >> >> that list is very dead. So apologies if anyone has read this before. >> >> >> >> I am trying to copy our storage server to a CephFS. We have 5 MONs in >> >> our cluster and (now) 7 MDS with max_mds = 4. The list (!) of files I >> am >> >> trying to copy is about 23GB, so it's a lot of files. I am copying them >> >> in batches of 25k using 16 parallel rsync processes over a 10G link. >> >> >> >> I started out with 5 MDSs / 2 active, but had repeated issues with >> >> immense and growing cache sizes far beyond the theoretical maximum of >> >> 400k inodes which the 16 rsync processes could keep open at the same >> >> time. The usual inode count was between 1 and 4 million and the cache >> >> size between 20 and 80GB on average. >> >> >> >> After a while, the MDSs started failing under this load by either >> >> crashing or being kicked from the quorum. I tried increasing the max >> >> cache size, max log segments, and beacon grace period, but to no avail. >> >> A crashed MDS often needs minutes to rejoin. >> >> >> >> The MDSs fail with the following message: >> >> >> >> -21> 2019-07-22 14:00:05.877 7f67eacec700 1 heartbeat_map >> is_healthy >> >> 'MDSRank' had timed out after 15 >> >> -20> 2019-07-22 14:00:05.877 7f67eacec700 0 mds.beacon.XXX Skipping >> >> beacon heartbeat to monitors (last acked 24.0042s ago); MDS internal >> >> heartbeat is not healthy! >> >> >> >> I found the following thread, which seems to be about the same general >> >> issue: >> >> >> >> >> http://lists.ceph.com/pipermail/ceph-users-ceph.com/2018-February/024944.html >> >> >> >> Unfortunately, it does not really contain a solution except things I >> >> have tried already. Though it does give some explanation as to why the >> >> MDSs pile up so many open inodes. It appears like Ceph can't handle >> many >> >> (write-only) operations on different files, since the clients keep >> their >> >> capabilities open and the MDS can't evict them from its cache. This is >> >> very baffling to me, since how am I supposed to use a CephFS if I >> cannot >> >> fill it with files before? >> >> >> >> The next thing I tried was increasing the number of active MDSs. Three >> >> seemed to make it worse, but four worked surprisingly well. >> >> Unfortunately, the crash came eventually and the rank-0 MDS got kicked. >> >> Since then the standbys have been (not very successfully) playing >> >> round-robin to replace it, only to be kicked repeatedly. This is the >> >> status quo right now and it has been going for hours with no end in >> >> sight. The only option might be to kill all MDSs and let them restart >> >> from empty caches. >> >> >> >> While trying to rejoin, the MDSs keep logging the above-mentioned error >> >> message followed by >> >> >> >> 2019-07-23 17:53:37.386 7f3b135a5700 0 mds.0.cache.ino(0x100019693f8) >> >> have open dirfrag * but not leaf in fragtree_t(*^3): [dir 0x100019693f8 >> >> /XXX_12_doc_ids_part7/ [2,head] auth{1=2,2=2} v=0 cv=0/0 >> >> state=1140850688 f() n() hs=17033+0,ss=0+0 | child=1 replicated=1 >> >> 0x5642a2ff7700] >> >> >> >> and then finally >> >> >> >> 2019-07-23 17:53:48.786 7fb02bc08700 1 mds.XXX Map has assigned me to >> >> become a standby >> >> >> >> The other thing I noticed over the last few days is that after a >> >> sufficient number of failures, the client locks up completely and the >> >> mount becomes unresponsive, even after the MDSs are back. Sometimes >> this >> >> lock-up is so catastrophic that I cannot even unmount the share with >> >> umount -lf anymore and a reboot of the machine lets the kernel panic. >> >> This looks like a bug to me. >> >> >> >> I hope somebody can provide me with tips to stabilize our setup. I can >> >> move data through our RadosGWs over 7x10Gbps from 130 nodes in >> parallel, >> >> no problem. But I cannot even rsync a few TB of files from a single >> node >> >> to the CephFS without knocking out the MDS daemons. >> >> >> >> Any help is greatly appreciated! >> >> >> >> Janek >> >> >> >> _______________________________________________ >> >> 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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