Some of your overhead is the Wal and rocksdb that are on the OSDs. The Wal
is pretty static in size, but rocksdb grows with the amount of objects you
have. You also have copies of the osdmap on each osd. There's just overhead
that adds up. The biggest is going to be rocksdb with how many objects you

On Mon, Feb 12, 2018, 8:06 AM Behnam Loghmani <>

> Hi there,
> I am using ceph Luminous 12.2.2 with:
> 3 osds (each osd is 100G) - no WAL/DB separation.
> 3 mons
> 1 rgw
> cluster size 3
> I stored lots of thumbnails with very small size on ceph with radosgw.
> Actual size of files is something about 32G but it filled 70G of each osd.
> what's the reason of this high disk usage?
> should I change "bluestore_min_alloc_size_hdd"? and If I change it and set
> it to smaller size, does it impact on performance?
> what is the best practice for storing small files on bluestore?
> Best regards,
> Behnam Loghmani
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> ceph-users mailing list
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