XFS: mkdir command gives: "mkdir: cannot create directory '###': No space left on device"

Issuing a mkdir command gives: "mkdir: cannot create directory '###': No space left on device"


umount /pgdata
mount -o inode64 /pgdata

edit /etc/fstab as below
/dev/vg_pgdata/lv_pgdata    /pgdata     xfs           inode64             1 0
By default in RHEL5 and RHEL6, xfs will only create inodes in disk blocks which result in inode numbers less than 2^32. If all of these low disk blocks are full, no more files can be created. Mounting with -o inode64 allows inodes to be created anywhere on disk. However, some 32-bit applications cannot handle 64-bit inode numbers.

RHEL7 will default to allowing 64-bit inode numbers.

Another possible cause is severely fragmented freespace. XFS allocates inodes in contiguous clusters of disk blocks; if no sufficiently large regions of freespace are available, no more inodes can be created.