RaidZ2 pool extend does not have full capacity

[keros]

Hello,
I’m using a homemade server with TrueNas scale latest version 24.10.0.2.

I had 4x 6Tb drive in a RaidZ2 pool with gave me 10.7 Tb of capacity. It was used à 97 %.
I used the expend new feature to increase my free space. I added a 5th drive of 6Tb. The capacity increased to 13.08 Tb. The RaidZ2 calculators I found indicates a 16.4 Tb with 5x 6Tb in RaidZ2.

I added a 6th 6Tb drive : the capacity increased to 15.73 Tb whereas the RaidZ2 calculators indicates 21,8 Tb with 6x 6Tb in RaidZ2.

Is it normal ?
Thanks

[scyto]

IIRC its a known bug in displaying the free space after an exend, i believe the bug is in upstream ZFS, if you search there is a post on it IIRC.

[Stux]

24.10 RC2 Raidz expansion caused miscalculated available storage

Seems like a mighty big gotchya with RaidZ expansion. This is the relevant bug report https://ixsystems.atlassian.net/browse/NAS-131728 Basically, the space available is calculated based on the original raidz width and 128k block size. This means that it is always going to be an underestimate once you add additionally disks. Oops. And that’s bascally all there is to it. I’m not sure of the consequences, but this seems problematic… and perhaps should be taken care of in the UI at least… if…

[keros]

@scyto

IIRC

I’ll look for that.
Thanks for the really quick reply !!

[keros]

I didn’t find this topic ;-(
Thank you for the link

[Protopia]

In essence if you use a shell and do a zpool list, it will show the correct sizes.

But the TN UI uses dataset stats and these are wrong. (I have proposed a change to fix this in Jira.)

[keros]

The zpool list indicates :
ZFS-6To 32.7T 21.0T 11.7T - - 0% 64% 1.00x ONLINE /mnt

So it seems that the percentage remaining free is good on the dashboard

Sorry, I was not able to put the screenshot in my fisrt post.

The space is available. It is enough for me. I won’t recreate it for sctrach > i’ll wait for an update.

Thank you all for your replies.

[Stux]

@keros

So it seems that the percentage remaining free is good on the dashboard

Yes.

There is talk about having the GUI calculate and display the correct (approximately) space available, since it can be figured out, even if the underlying tooling doesn’t know, but at least the percentage is correct.