[Lustre-discuss] Poor metadata operation performance

[Ken Hornstein]

>Ken, the OSTs need to track the ownership of objects for quota.  The more
>stripes there are on a file, the more RPCs that need to be sent, which is why
>we don't recommend wide striping unless there is a reason for it (bandwidth,
>size, etc).

Fair enough; I always forget about quota accounting, because we never use
it.  But I'm wondering why this in particular causes such a hit, because
the MDS sends the setattr RPCs asynchronously; in theory it should just
fire them off and not have to wait until they're done.  Perhaps it's the
overhead of sending those RPCs which is slowing things down?  I could believe
that, although I would have thought that it wouldn't be that bad.

--Ken