Re: [List] Cannot find out what uses space in ZFS dataset

From: Andrea Venturoli <ml_at_netfence.it>
Date: Thu, 18 Sep 2025 17:39:44 UTC
On 9/18/25 18:44, freebsd@vanderzwan.org wrote:

>>> zroot/ROOT/default@auto_zroot-20250611020000            3.34G   209M          -       -              -         -
>>> zroot/ROOT/default@auto_zroot-20250711020000            62.2G   407M          -       -              -         -
> 
> Here the refer jumps from 3.34 to 62.2 GB, so it looks like your missing data is in this snapshot.

Hmmm...

> # zfs list  -o name,refer,used,usedbysnapshots|grep default
> zroot/ROOT/default             62.1G  70.5G     8.36G

usedbysnapshots is 8.36G, so I guess this single snapshot cannot take 60GB.
Also "zfs send" doesn't transmit snapshots, so, even if this was true, 
it should not produce such a big amount of data.



> I guess  'zfs diff zroot/ROOT/default@auto_zroot-20250611020000  zroot/ROOT/default@auto_zroot-20250711020000'  can show what happened.

I know what happened on that day: I did a big upgrade of the system.
However, I've done this hundreds of times on several boxes and never 
incurred in this problem.




In any case, I tried deleting the 20250711020000 snapshot.
Now the jump in refer just moved to the next:>  zfs list -t all -o 
name,refer,used,usedbychildren,usedbydataset,usedbyrefreservation,usedbysnapshots|grep 
default
> zroot/ROOT/default                                      62.1G  70.5G         0B   62.1G             0B     8.36G
> ...
> zroot/ROOT/default@auto_zroot-20250611020000            3.34G   215M          -       -              -         -
> zroot/ROOT/default@auto_zroot-20250810020000            62.1G   116M          -       -              -         -
> ...
Still "zfs send" generates the same huge amount of data.





  bye & Thanks
	av.