Upgrade disks or copy pool

[SBM]

Hi all,

I have a freenas box with 8 2tb disks in raidz2.
The pool is at 85% so I have 8 4tb disks on the way.

I can take the pool offline for a few days to the upgrade.
At the moment I see 2 ways to do this:
#1: Replace 2tb with 4tb one at a time and resilver
#2: Create a new pool with the 4tb disks and just copy (I have the sata ports for this)

What's the best way to do this?
Or do you guys recommend another approach?

Thanks

 

[tvsjr]

Since you have the SATA ports, are you planning to keep the 2TB drives in service? If so, just add the 8x4TB vdev to your existing pool and move nothing...

 

[SBM]

No I'm not planning to keep the 2tb's.
I don't need the storage and the disks won't fit in the current case.

 

[depasseg]

I would create a new pool with the 4TB drives, snapshot the existing pool, replicate and migrate your shares and other settings. I actually have a thread outlining the steps around here somewhere.

 

[tvsjr]

^^ +1. Less chances for failure by bringing the new pool online and migration via replication, versus resilvering 8 times.

 

[SBM]

Ok, last night I ended up reading some more and found this in the 9.3 docs

1. Shut down the system.
2. Install one new disk.
3. Start up the system.
4. Go to Storage ‣ Volumes, select the pool to expand and click the “Volume Status” button. Select a disk and click the “Replace” button. Choose the new disk as the replacement.
5. You can view the status of the resilver process by running zpool status. When the new disk has resilvered, the old one will be automatically offlined. You can then shut down the system and physically remove the replaced disk. One advantage of this approach is that there is no loss of redundancy during the resilver.

This method seems to be new in 9.3 and does not degrade the pool.
I would guess that this is much faster and doesn't stress the pool that much because it's just a straight copy of an existing drive.
Is this true or does freenas resilver the new drive with the 7 others?

 

[Ericloewe]

This method seems to be new in 9.3 and does not degrade the pool.

I'm fairly certain it's not new. Just a bit hidden.

I would guess that this is much faster and doesn't stress the pool that much because it's just a straight copy of an existing drive.
Is this true or does freenas resilver the new drive with the 7 others?

It's always a full-blown resilver.

 

[depasseg]

It's always a full-blown resilver.

And it will need to be done 8 times.

Since you are already at 85%, you probably have a decent amount of fragmentation. Replicating to a new pool will do a better job at resolving that.