Preconditioning an RBD image

[Alex Gorbachev <ag@xxxxxxxxxxxxxxxxxxx>]

I wanted to share the recent experience, in which a few RBD volumes, formatted as XFS and exported via Ubuntu NFS-kernel-server performed poorly, even generated an "out of space" warnings on a nearly empty filesystem.  I tried a variety of hacks and fixes to no effect, until things started magically working just after some dd write testing.

The only explanation I can come up with is that preconditioning, or thickening, the images with this benchmarking is what caused the improvement.

Ceph is Hammer 0.94.7 running on Ubuntu 14.04, kernel 4.10 on OSD nodes and 4.4 on NFS nodes.

Regards,

Alex

Storcium

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Alex Gorbachev

Storcium

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