xfs project quota question

[Christoph Hellwig]

On Thu, Jul 30, 2009 at 11:49:54AM +0200, Erik Gulliksson wrote:
> Hi,
> 
> We have recently started to use XFS for our production storage servers
> (coming from ZFS and Lustre/ext3) and are now considering activating
> project quota on quite massive scale. For our setup there would be
> between 10k and 100k "project directories" per filesystem, each with
> up to 1T data and up to 1M number of files. Would this even be
> feasible to consider? Have anyone done any tests with a big number of
> project quotas for an xfs file system? How well does it scale?

Project quotas scale exactly the same way as user or group quotas.  10k
different IDs defintively should be fine.  100k different IDs might run
into scaling problems with the in-core quota hash, but that's something
only limited by choice of a hash-table for the in-memory lookup and
could be easily fixed by switching to a smarter data structure which we
could fix short-term given sufficient enough interest.