On Mon, Jan 21, 2019 at 12:52 AM Yan, Zheng <uker...@gmail.com> wrote:
> On Mon, Jan 21, 2019 at 12:12 PM Albert Yue <transuranium....@gmail.com> > wrote: > > > > Hi Yan Zheng, > > > > 1. mds cache limit is set to 64GB > > 2. we get the size of meta data pool by running `ceph df` and saw meta > data pool just used 200MB space. > > > > That's very strange. One file uses about 1k metadata storage. 560M > files should use hundreds gigabytes. > That's presumably because OSDs still don't report LevelDB/RocksDB usage up in that view, and all the MDS metadata is stored there? -Greg > > > Thanks, > > > > > > On Mon, Jan 21, 2019 at 11:35 AM Yan, Zheng <uker...@gmail.com> wrote: > >> > >> On Mon, Jan 21, 2019 at 11:16 AM Albert Yue <transuranium....@gmail.com> > wrote: > >> > > >> > Dear Ceph Users, > >> > > >> > We have set up a cephFS cluster with 6 osd machines, each with 16 8TB > harddisk. Ceph version is luminous 12.2.5. We created one data pool with > these hard disks and created another meta data pool with 3 ssd. We created > a MDS with 65GB cache size. > >> > > >> > But our users are keep complaining that cephFS is too slow. What we > observed is cephFS is fast when we switch to a new MDS instance, once the > cache fills up (which will happen very fast), client became very slow when > performing some basic filesystem operation such as `ls`. > >> > > >> > >> what's your mds cache config ? > >> > >> > What we know is our user are putting lots of small files into the > cephFS, now there are around 560 Million files. We didn't see high CPU wait > on MDS instance and meta data pool just used around 200MB space. > >> > >> It's unlikely. For output of 'ceph osd df', you should take both both > >> DATA and OMAP into account. > >> > >> > > >> > My question is, what is the relationship between the metadata pool > and MDS? Is this performance issue caused by the hardware behind meta data > pool? Why the meta data pool only used 200MB space, and we saw 3k iops on > each of these three ssds, why can't MDS cache all these 200MB into memory? > >> > > >> > Thanks very much! > >> > > >> > > >> > Best Regards, > >> > > >> > Albert > >> > > >> > _______________________________________________ > >> > 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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