On 5/29/19 5:40 AM, Konstantin Shalygin wrote:
> block.db should be 30Gb or 300Gb - anything between is pointless. There
> is described why:
> http://lists.ceph.com/pipermail/ceph-users-ceph.com/2019-February/033286.html

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)

regards,
Mattia


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