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Stragic Enlargening of a VDev

Macaroni323

Explorer
Joined
Oct 8, 2015
Messages
60
I have a pool that I've just expanded to 3 VDevs of 2 x 4TB mirrored disks each for a total of 12TB. I have come into 2 8TB disks and I'd like to change one of the VDevs from 2 v4TB into 2 x 8TB and save the 4TB disks as backups for the 4TB mirrors (two are very old so...). I want to know if it is possible to pull a 4TB disk from one of the 2 x 4TB mirrors, replace with an 8TB, allow the system to resilver (probably at 4TB of the 8TB if it is possible), after the resilvering replace the remaining 4TB disk mirrored with the 8TB with the other 8TB and resilver (probably resulting in a 2 x 8TB partitioned only to 4TB mirror). After all is stable I'd like to expand the partition.

Is this feasible?
 

Arwen

MVP
Joined
May 17, 2014
Messages
3,509
Yes, that is a standard function of ZFS.

Yes, ZFS will only re-silver the amount of used data on the 4TB vDev to the new 8TB disk.

No, TrueNAS will not make a 4TB partition on your 8TB disks. They will be 8TB in size.

TrueNAS, Core or SCALE, will by default automatically expand the vDev after both 4TB disks in a vDev are replaced with larger disks, (8TB in your case).

You can even maintain full 2 way redundancy with a replace in place. This requires an addition disk slot for the new 8TB drive. But, if you don't have the addition disk slot, you can certainly perform the regular replace.

See manual for replacing a disk.
 

danb35

Hall of Famer
Joined
Aug 16, 2011
Messages
15,278
No, TrueNAS will not make a 4TB partition on your 8TB disks.
Well, it shouldn't--but there's a bug in the current release of SCALE that does this, at least under some circumstances. AFAIK CORE is unaffected.
 

Macaroni323

Explorer
Joined
Oct 8, 2015
Messages
60
Thanks for the help... I will not be able to expand my pool after all (maybe others will find this thread useful). I have tested the two 8TB disks and one is perfectly fine but the other failed WD Data Lifeguard Diags with bad sectors. They were able to be repaired so the disk currently (when restested) passes all the WD Data Lifeguard tests but I not willing to put it in my TrueNAS server. SMART counts look scary.
 

Etorix

Wizard
Joined
Dec 30, 2020
Messages
2,011
SMART errors are a ground for RMA if the drive is still under warranty.
 
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