Hello,

using unRAID 7.2.3. Tried to create a dataset with recordsize 1M. But it's not possible to create or to set:

cannot create 'BKUP4/bkp_Tank': 'recordsize' must be power of 2 from 512B to 128K

Upon researching, i found that module parameter zfs_max_recordsize needs to be set accordingly.

Can you please advise how i can do this in unRAID? Thankyou.

(And what might be the reason for this limitation?)

Edited February 8Feb 8 by unraidinterested

ok, i found out that in Tools/System drivers i can add the parameter, save and reboot.

However, this does not fix the issue.

How can i create 1M recordsize datasets in unRAID?

You should just need to type zfs set recordsize=1M pool/dataset

If that's not working, there's something else going on, start by posting the diags.

That's not working either.

root@Unraid:~# zfs create BKUP4/bkp_Temp

root@Unraid:~# zfs set recordsize=1M BKUP4/bkp_Temp

cannot set property for 'BKUP4/bkp_Temp': 'recordsize' must be power of 2 from 512B to 128K

I see that in Diags even though allegedly it's anonymized, SN of all disks are included in clear text. I feel a little bit uneasy without redacting the files or at least checking what is in them. Is there some specific file you are asking for?

(The installation was upgraded from when i bought my first license which was probably in November 2024, so maybe 6.7...; some tools are installed like ZFS Master)

Edited February 8Feb 8 by unraidinterested

with a little test, i can add that setting a testdataset on a ZFS pool to 1M works.

So it might have to do with the single SATA drive BKUP4, running as unassigned device in unRAID (the unassigned devices plugin is installed)?

Edited February 8Feb 8 by unraidinterested

found the issue:

when creating the pool, a lot of features are not set, including the large_block feature, most likely due to compatibility. Once you run zpool upgrade <Pool>, the necessary features are set and i was able to set recordsize=1M. (This implies, you will not be able to mount the pool on ZFS systems not supporting the featureset).

57 minutes ago, unraidinterested said:

when creating the pool, a lot of features are not set, including the large_block feature, most likely due to compatibility.

This was with UD right? All features will be enabled for pools created with Unraid.

affirmative. I knew there was a feature set, but i was missing the info that UD has its own approach. Once you think about it and consider that it deals with external disks that you just want to mount without modifying anything, it makes a lot of sense.

In my usecase, my unRAID has a cage for single drives to send/recv zfs snapshots for backup purposes but now i know what to do.