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

On 9/21/25 10:07, Andrea Venturoli wrote:
> On 9/19/25 15:28, freebsd@vanderzwan.org wrote:
> 
>> Maybe procstat -af and look for a regular file with a huge value in 
>> OFFSET column. That assumes the file offset is at EOF for that huge file.
> 
> Didn't help.
> 
> I finally had the chance to reboot, but not even this solved!!! :(
> 
> I still get the same figures:
>> # du -d 0 -h -x
>> 3.3G    .
>> # zdb -ddd zroot/ROOT/default 0:-1:A |sort -h -b -k 5 |tail
>>     186544    2   128K   128K  31.3M     512  57.5M  100.00  ZFS plain 
>> file
>>       5738    2   128K   128K  33.2M     512  51.9M  100.00  ZFS plain 
>> file
>>          0    6   128K    16K  39.5M     512   176M   29.37  DMU dnode
>>     186545    2   128K   128K  48.4M     512  93.5M   99.60  ZFS plain 
>> file
>>     186426    2   128K   128K  53.1M     512   101M  100.00  ZFS plain 
>> file
>>     186668    3   128K   128K  76.2M     512   178M  100.00  ZFS plain 
>> file
>>     186209    3   128K   128K  91.9M     512   253M  100.00  ZFS plain 
>> file
>>     186671    3   128K   128K   135M     512   327M  100.00  ZFS plain 
>> file
>>     186427    3   128K   128K   140M     512   334M  100.00  ZFS plain 
>> file
>>        360    3   128K   128K  58.8G     512  90.0G  100.00  ZFS plain 
>> file
> 
> 
>   bye & Thanks
>      av.


Have you done a scrub recently?


I had the idea to use diff(1) to compare the snapshots when the size 
jumped, but did not post it because if du(1) cannot see problem file(s) 
then diff(1) should not:

# diff -r /.zfs/snapshot/auto_zroot-20250611020000 
/.zfs/snapshot/auto_zroot-20250711020000


An improved idea that might work would be to use zfs-diff(8) to compare 
the snapshots.  Consider adding option "-H" and redirecting the output 
to a file for further analysis, issue tracking, etc.:

# zfs diff @auto_zroot-20250611020000 
zroot/ROOT/default@auto_zroot-20250711020000


Perhaps booting into single user mode, doing a scrub, and investigating/ 
trouble-shooting?


Perhaps booting live media, doing a scrub, and investigating/ 
trouble-shooting??


Do you have a saved zfs-send(8) backup stream or raw disk image from 
prior to the issue that you can restore?


If all else fails, backup/ wipe/ install/ restore the OS disk.  I prefer 
the oldest supported version of an OS (e.g. FreeBSD-13.5-RELEASE), as it 
should have fewer bugs than newer versions of an OS.


David