Strange case of deleting lots of files and "df" not recognizing it....(unless I umount/mount) the disk...

[Linda Walsh]

This isn't that big of a deal, as I'm not close to the limit,
but I pruned a backup disk that was at 87% full (1.5T free), down
by 3.8T.  Indeed, doing a 'du' of the disk shows space is ~6-7T (/11T)
but df still shows 9.5T usage.

I've done sync a few times, but the files were deleted almost a half an hour
ago.

So when does it actually synchronize w/o me forcing it?  (I.e. umount/mount)?

Have seen this before, and that's what brought it into 'sync'....

none of the xfs_centitimes are greater than 3000 or 30 seconds.  Not a big
problem that I know of, hardly a problem at all, cept that it is weird.

Curious?
-linda