By default, with 32bit inodes, XFS places inodes only in the first 1TB of a disk. If you have a disk with 100TB, all inodes will be stuck in the first TB. This can lead to strange things like "disk full" when you still have plenty space free, but there's no more place in the first TB to create a new inode. Also, performance sucks.
To come around this, use the inode64 mount options for filesystems >1TB. Inodes will then be placed in the location where their data is, minimizing disk seeks.
Beware that some old programs might have problems reading 64bit inodes, especially over NFS.
This can be corrected with a small update from the support team.