about 15 years ago I experienced the same thing. An updater script based on rsync was trying to keep one nfs machine image in sync with another. However for what ever reason, the script accidentally tries to sync the entire nfs root directory with its own, deleting everything show by show in reverse alphabetical order.

At the time Lustre didn't really have any good monitoring tools for showing you who was doing what, so they had to wait till they hit a normal NFS server before they could figure out and stop what was deleting everything.

Needless to say, a lot of the backups may have been failing.