I recently set up a Lustre 2.8 file system that uses ZFS for the backend storage (both on the MDT and OSTs). When I was doing some testing, I noticed that the output from lfs quota seemed odd. While the quota information for the amount of used space seemed correct, the info on the number of files was off. For example, when I started with no files, “lfs quota” showed this:

Filesystem kbytes quota limit grace files quota limit grace
/lustre/xxxxx
33 0 0 - 18446744073709551595 0 0 -

As I created empty files one-by-one, the number of files kept incrementing. Once I had 21 files created, lfs quota then reported that I had zero files:

Filesystem kbytes quota limit grace files quota limit grace
/lustre/xxxxx
211 0 0 - 0 0 0 -

It looks like some kind of counter under/overflow, but I am not sure if this is an issue with Lustre or with ZFS.