ZFS vs. df -h completely different size of filesystem [solved]

[Josh Carter]

Miroslav,

> But space remains occupied by data of snapshots! Thats why df showed  
> just 24G size and not 360G. Df knows nothing about snapshots.

Some additional factors to keep in mind when looking at ZFS and used/ 
available disk space:

- Snapshots (as you discovered).

- Compression: when compression is turned on (as you have), you can't  
know exactly how much more data will fit into the filesystem because  
it depends on how well the data compresses.

- Sparse files: "ls -h" will show you how large a file says it is; "du  
-h" and "zfs list" should show how much space is actually used. These  
will disagree on sparse files.

- Space reserved for copy-on-write: "zpool list" and "zfs list" will  
differ on available space because ZFS reserves some amount of slop  
space; truly running out of blocks is disastrous in a COW system.

In general, learn to trust "zfs list" because the traditional tools  
don't know the full story.

Best regards,
Josh