Hi Konstantin! Quoting Konstantin Shalygin (k0ste@xxxxxxxx): > >Is there any recommandation of how many osds a single flash device can > >serve? The optane ones can do 2000MB/s write + 500.000 iop/s. > > Any sizes of db, except 3/30/300 is useless. I have this from Mattia Belluco in my notes which suggests that twice the amount is best: > Following some discussions we had at the past Cephalocon I beg to differ > on this point: when RocksDB needs to compact a layer it rewrites it > *before* deleting the old data; if you'd like to be sure you db does not > spill over to the spindle you should allocate twice the size of the > biggest layer to allow for compaction. I guess ~60 GB would be the sweet > spot assuming you don't plan to mess with size and multiplier of the > rocksDB layers and don't want to go all the way to 600 GB (300 GB x2) Source is http://lists.ceph.com/pipermail/ceph-users-ceph.com/2019-May/035086.html. And apart from the RocksDB pecularities the actual use case also needs to be considered. Lots of small files on a CephFS will require more DB space than mainly big files as Paul states in the same thread. Cheers, LF. -- Lars Fenneberg, lf@xxxxxxxxxxxxx _______________________________________________ ceph-users mailing list ceph-users@xxxxxxxxxxxxxx http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
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