I have a FreeNAS system with one pool, consisting of two mirrored vdevs: a total of 4 4TB drives, so 8TB usable space. I use the system mainly for storing media files and backups at home, not for any high-performance or multiple-user needs. My case has 8 drive bays, so I have room for four more drives. This has been working fine for a few years, and I'm not facing an emergency situation, but it's probably time to consider expanding things before space does get tight.
The docs discuss this a bit in the Replacing Disks to Grow a Pool section, but it appears to miss a main concern: the preferred method is said to be adding vdevs, with the replacing-disk solution only used if you don't have any spare disk ports. However, it seems to me that even if I do have the ports (which I do), I wouldn't want to use them. If I get two larger drives and add a new mirrored vdev, I'd then have a pool with six drives, four of which are smaller-capacity and older, but I can't remove any of them because you can't remove a vdev (I think)--so I'd have to maintain six drives going forward.
I'd think that the right approach would be to follow the advice in the Replacing-Disks section to replace one vdev. I can then maintain four drives, but with more space; alternately I could leave the two existing drives in place and create a new pool from them, for some different storage task.
Does that make sense? And, this may be a(nother) silly question, but I'd get the space even by replacing only one vdev, right? That is, if I get two 8TB disks and use them to replace one vdev, I'd get more space; I don't have to get four drives to replace both mirrored vdevs?
The docs discuss this a bit in the Replacing Disks to Grow a Pool section, but it appears to miss a main concern: the preferred method is said to be adding vdevs, with the replacing-disk solution only used if you don't have any spare disk ports. However, it seems to me that even if I do have the ports (which I do), I wouldn't want to use them. If I get two larger drives and add a new mirrored vdev, I'd then have a pool with six drives, four of which are smaller-capacity and older, but I can't remove any of them because you can't remove a vdev (I think)--so I'd have to maintain six drives going forward.
I'd think that the right approach would be to follow the advice in the Replacing-Disks section to replace one vdev. I can then maintain four drives, but with more space; alternately I could leave the two existing drives in place and create a new pool from them, for some different storage task.
Does that make sense? And, this may be a(nother) silly question, but I'd get the space even by replacing only one vdev, right? That is, if I get two 8TB disks and use them to replace one vdev, I'd get more space; I don't have to get four drives to replace both mirrored vdevs?