ZFS ZFS - used/avail magic

[rootbert]

Hi folks,

I just deleted the contents of a ZFS dataset and found some information which seems weird to me, maybe I missed something and someone of you could enlighten me.
Before deletion, "zfs list" showed me "USED 285G, AVAIL 775G, REFER 285G". I did not have a snapshot, and deleted everything under that dataset with "rm -Rf *" - the content were disk images of notebooks made with dd but also the disk contents of MS Windows partitions (users files). After deletion, I got "USED 336K, AVAIL 633G, REFER 336K". How is that?

Also: I cannot destroy the dataset because it says "cannot unmount '/storage/2017ex': Device busy" - fstat and lsof not listing any open files. This is a FreeBSD 12.0 machine.

 

[rootbert]

I just discovered that my colleague made a checkpoint in January ... maybe this weird information was showing due to that fact.

 

[unitrunker]

I just discovered that my colleague made a checkpoint in January ...

You can delete the snapshot if no longer needed.

 

[rootbert]

You can delete the snapshot if no longer needed.

Snapshots are not to be confused with checkpoints. I deleted the checkpoint. However, it's still not clear to me why deleting files before the checkpoint cost me roughly 150GB instead of freeing that amount.