Adding used drives back to NAS

[Karnage]

My NAS has 4 bays.

I started with 3 x 2tb drives in raidz and last year replaced them one by one with 3tb drives over a few days.

Since then I have found a way to expand the NAS to hold 6 drives in total, and I want to add the original 3 x 2tb drives back in.

My question is about what to expect when I add them back and power up the NAS. I know freenas can recognise zfs pools, but this pool would have gotten broken as the disks were removed at different times. So if I try to add them as a new vdev, will the previous raidz vdev show up? Should I format them first?

I have other questions too, while I think of them, but I havent started searching for these answers yet.

Should I add the 3 older disks (as a vdev) to the existing pool, or create a new pool?
I have two main datasets and one could be moved to the new pool. Would that help in any way?
- The current pool is about 88% full.
- I store family photos on the current zpool, and am thinking that if I had a separate zpool I could maintain a local copy of that folder that wouldnt be susceptible to multiple harddisk failure.
If I do add the vdev to the pool, would there be any benefit to copying the largest folders to a new location to have them written to the empty vdev?

Thanks in advance.

 

[Rilo Ravestein]

I have other questions too, while I think of them, but I havent started searching for these answers yet.

Should I add the 3 older disks (as a vdev) to the existing pool, or create a new pool?
I have two main datasets and one could be moved to the new pool. Would that help in any way?
- The current pool is about 88% full.
- I store family photos on the current zpool, and am thinking that if I had a separate zpool I could maintain a local copy of that folder that wouldnt be susceptible to multiple harddisk failure.
If I do add the vdev to the pool, would there be any benefit to copying the largest folders to a new location to have them written to the empty vdev?

You store family pictures on a RAIDZ pool? I assume you have another backup of those pictures somewhere else too? RAIDZ is not a good choice for important data: http://www.zdnet.com/article/why-raid-5-stops-working-in-2009/
Also read this: https://forums.freenas.org/index.ph...ning-vdev-zpool-zil-and-l2arc-for-noobs.7775/
Then you can decide on creating a new zpool or adding a new vdev to the existing one.

 

[Robert Trevellyan]

Should I format them first?

If ZFS detects partition tables on the drives it may refuse to use them, so it's probably best to wipe them first.

The current pool is about 88% full.

Then you need to add capacity sooner rather than later.

There would be some benefits to adding the new drives as a 2nd pool, particularly the flexibility, but you'll probably be better off long term if you figure out a way to transition to a 6-drive RAIDZ2 pool. This will involve moving all your data off your existing pool and destroying it.

Unless your data is backed up elsewhere, a mostly full pool of large drives in RAIDZ1 is pretty risky.

 

[Karnage]

I assume you have another backup of those pictures somewhere else too?

Of course :). In two different geographic locations and one online.

I did read that guide, which is why I didnt just add the disks in a new vdev already.

 

[Karnage]

If ZFS detects partition tables on the drives it may refuse to use them, so it's probably best to wipe them first.

There would be some benefits to adding the new drives as a 2nd pool, particularly the flexibility, but you'll probably be better off long term if you figure out a way to transition to a 6-drive RAIDZ2 pool.

Second pool it is then. And I know RAIDZ2 would be better, but I have 3 x 3tb disks and 3 x 2tb ones.

 

[anodos]

Second pool it is then. And I know RAIDZ2 would be better, but I have 3 x 3tb disks and 3 x 2tb ones.

Using those disks to make 2 * raidz1 vdevs yields ~10TB

Using those disks to make 1*raidz2 vdev yields ~10TB.

The optimal choice is pretty clear. Go with 2* 3-way mirrors. :)

 

[Rilo Ravestein]

1 raidz2 with 6x2TB = 8TB. All disks in the same array means all disks wil use the size of the smallest one

 

[Robert Trevellyan]

1 raidz2 with 6x2TB = 8TB. All disks in the same array means all disks wil use the size of the smallest one

This is correct, but the OP could plan to replace the 2TB drives one at a time, eventually yielding a higher capacity pool with better redundancy. But it seems he understands the risks of RAIDZ1 and has enough backups to avert disaster.