[ceph-users] Raw space usage in Ceph with Bluestore

Glider, Jody j.glider at sap.com
Wed Nov 28 13:27:49 PST 2018


I’m trying to find a way to determine real/physical/raw storage capacity usage when storing a similar set of objects in different pools, for example a 3-way replicated pool vs. a 4+2 erasure coded pool, and in particular how this ratio changes from small (where Bluestore block size matters more) to large object sizes.

I find that ceph df detail and rados df don’t report on really-raw storage, I guess because they’re perceiving ‘raw’ storage from their perspective only. If I write a set of objects to each pool, rados df shows the space used as the summation of the logical size of the objects, while ceph df detail shows the raw used storage as the object size * the redundancy factor (e.g. 3 for 3-way replication and 1.5 for 4+2 erasure code).

Any suggestions?

Jody Glider, Principal Storage Architect
Cloud Architecture and Engineering, SAP Labs LLC
3412 Hillview Ave (PAL 02 23.357), Palo Alto, CA 94304
E   j.glider at sap.com<mailto:j.glider at sap.com>, T   +1 650-320-3306, M   +1 650-441-0241

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