No subject

the initial filesystem.  If the filesystem was big enough to begin
with (i.e.  using maximally sized AGs at mkfs time) then growing it
will result in a layout exactly the same as if it was mkfs'd at full
size.

However, the allocation patterns will be significantly different
between the two filesystems, so there will be no similarity in data
layout between the two different filesystems.

> and have roughly the
> same performance characteristics?

See previous answer.

> Assume, for sake of argument, that the
> file system was grown before space got tight enough to cause any
> severe large file fragmentation.

See previous answer. ;)

> I've been under the impression that one gained some performance benefits if one
> laid out the whole file system at once  is that a mis-impression?

I wouldn't say you "gain performance benefits" by starting with a
larger filesystem, more that a grown filesystem has different aging
characteristics to one that has not been grown. See previous answer.
;)

> That asked/said...is there any work underway to create an xfs_shrinkfs, so
> that one could go the other way?

http://xfs.org/index.php/Shrinking_Support

Cheers,

Dave.
-- 
Dave Chinner
david at fromorbit.com