> I have a 30TB XFS filesystem created on CentOS 5.4 X86_64,
> kernel 2.6.39, using xfsprogs 2.9.4. [ ... ] The filesystem
> contains a MongoDB installation consisting of roughly 13000
> 2GB files which are already allocated. [ ... ]
BTW, while 30TB is probably still in the real of the plausible
if excessively large, and this is a 64b system, this is a good
example of a gratuitously large filetree and an excessively wide
RAID set under it.
A large single filetree only makes sense if one need a large and
unified free space pool... But in this application all files are
essentially independent and preallocated.
A more manageable setup might have been a set of 4-8TB
filetrees, for example on a group of 3TBx 2+1 or even 4+1 (split
in two partitions) RAID5 sets.