On Thu, Mar 16, 2017 at 11:12 AM, TYLin <wooertim@xxxxxxxxx> wrote: > Hi all, > > We have a CephFS which its metadata pool and data pool share same set of OSDs. According to the PGs calculation: > > (100*num_osds) / num_replica That guideline tells you rougly how many PGs you want in total -- when you have multiple pools you need to share it out between them. As you suggest, it is probably sensible to use a smaller number of PGs for the metadata pool than for the data pool. I would be tempted to try something like an 80:20 ratio perhaps, that's just off the top of my head. Remember that there is no special prioritisation for metadata traffic over data traffic on the OSDs, so if you're mixing them together on the same drives, then you may see MDS slowdown if your clients saturate the system with data writes. The alternative is to dedicate some SSD OSDs for metadata. John > > If we have 56 OSDs, we should set 5120 PGs to each pool to make the data evenly distributed to all the OSDs. However, if we set metadata pool and data pool to both 5120 there will have warning about “too many pgs”. We currently set 2048 to metadata pool and data pool but it seems data may not evenly distribute to OSDs due to no sufficient PGs. Can we set a smaller PGs to metadata pool and larger PGs to data pool? E.g. 1024 pg to metadata and 4096 to data pool. Is there a recommend ratio? Will this result in any performance issue? > > Thanks, > Tim > _______________________________________________ > ceph-users mailing list > ceph-users@xxxxxxxxxxxxxx > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com _______________________________________________ ceph-users mailing list ceph-users@xxxxxxxxxxxxxx http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
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