Question about RAIDZ Size

[Albert Utah]

Hello FreeNAS community,

1) I love freeNAS, it just works for my family backup needs. Thank you freeNAS.org;

2) a question about the RAIDZ size. There are 6 HDDs, two 500GB, two 2TB and two 4TB. I know those are not optimized for RAIDZ setting, but still surprised to see that there is only 2TB for the RAIDZ result. Is this normal?

I have checked my BIOS setting up, and sure it is in AHCI mode.

 

[Kris Moore]

Since you're using a mix of drive sizes, it sounds like you are ending up with 500G being the limiting factor.

I.E. if you are on raidz2, you get 6 Drives, of 500G each, minus 2 Parity == 2TB.

If you use matching drive sizes (as is best practice) then you should unlock the full capacity of all the disks.

 

[Albert Utah]

Thank you. Maybe I should just put six 4TB to use.

 

[Chris Moore]

Thank you. Maybe I should just put six 4TB to use.

Basically, ZFS is limiting the capacity of all the drives to the size of the smallest drive. If you are not prepared to replace all the drives at once, or if you have already put data into the pool, you can grow the capacity by replacing the 500GB drives (one at a time) with 4TB drives and once they are both replaced the pool will behave as if all drives are at the 2TB size. Later, you can replace the two 2TB drives (again, one at a time) with 4TB drives. Once all drives are at the 4TB size, you will have the full capacity of the pool available.

Here is a link to a relatively accurate calculator for determining the capaity of the pool:

a useful ZFS capacity calculator tool:
https://wintelguy.com/zfs-calc.pl

 

[Albert Utah]

Thank you so much for the quick response and useful link.