Temporarily using larger drives in RAIDZ2 and then replacing with smaller drives

[cods4]

I have a new server arriving shortly and will be migrating my data and some of my drives to the new machine. So I'm currently planning my vdev structure and how I will do the migration. The main vdev will be a RaidZ2 with 8 drives.

My question is around the sizes of the drives; I currently have 6 x 3TB drives and 1 x 4TB drive which are destined for this vdev, however I obviously need one more drive.

What I am wanting to do is use a spare 8TB drive as the 8th drive in this vdev, but only temporarily until I have the budget for another drive. I will then replace it with a 4TB drive. My concern is around whether this will work, can the 8TB drive be replaced with a 4TB drive down the track?

I understand that my pool size will be limited by the 3TB drives, so none of the drives will ever have more than 2.7TiB of data on them. But I also note that the manual says you cannot replace a drive in a Raidz pool with a smaller one. I'm just not sure if this rule will apply in my case where the replacement drive is still larger than the smallest drive in the pool.

System specs
SuperMicro SuperStorage 6027R-E1R12T 12x3.5" bays
Intel Xeon E2620v2 CPU
16GiB ECC RAM (soon to be upgraded to 32 or 64GiB)
X540 Dual Port 10GBase-T NIC
On board LSA 2208 Raid Controller - If I cant flash to IT mode then i will get an IBM M1015 in IT mode.

 

[Stux]

I *think* you can do what you want.

I *think* I've done it before. As long as the pool hasn't expanded, you can use a drive smaller than a current drive, as long as the pool hasn't expanded to use more.

Alternatively, you could partition the 8TB drive, but i really *think* it should work the way you think.

 

[Ericloewe]

I *think* you can do what you want.

I *think* I've done it before. As long as the pool hasn't expanded, you can use a drive smaller than a current drive, as long as the pool hasn't expanded to use more.

Alternatively, you could partition the 8TB drive, but i really *think* it should work the way you think.

+1 on this, minus the having tried it part.

I'm pretty sure that you'll be fine, but you can partition the disk manually to be sure.

 

[cods4]

Thanks for the replies guys. I think I will just give it a go without partitioning. That way I can report back here on whether it worked or not.