Hi there,
I read about how striping of rbd works at http://ceph.com/docs/next/man/8/rbd/
and it seems rather complex to me. As the individual objects are placed randomly
over all osds taking crush into account anyway, what's the benefit over simply
calculating object_id = (position / chunk_size).to_i or even faster with
object_id = position >> order?
I also wonder what object size is recommended for vm images? I assume the
default of 4 MB is not optimal, something bigger like 64 MB would be much better
as it'd require much fewer objects (less overhead on osds' filestores) and much
fewer client-osds roundtrips (reads/ write from/ to different rados objects) for
most vm workloads? The distribution should still be ok, as most vm images are
several GB and so still have several hundrets or thousands of objects with 64MB
objects? Are there any benchmarks available for this? :)
Cheers,
Corin
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