SOLVED Replacing both SMR disks in Unhealthy pool

[Computer8080]

This post is about double checking my plans and more importantly hopefully help people with similar SMR disk problems in the future.

The backstory:
Two years ago I got an old unused computer, bought drives and made it into na FreeNAS server. I didn't want to spent too much, because this was the first thing I was playing with NASes and RAID etc.. Unfortunately the drives I bought were Seagate Baracuda 2 TB (knowing they're not really intended for this, but I thought they would be good enough) which one year later turned out to be SMR drives (Thanks Seagate....). I put the two drives in a MIRRORed pool with 1 vdev. In March this year, one of the drives reported 9 uncorrectable sectors but no data was lost due to the MIRROR. The drive was 2 moths before end of warranty so I RMA'd it hoping it was just bad luck and rebuilt the pool with the new drive. Today the other original drive reported 16 uncorrectable sectors, again with no data loss. The drive is out of warranty and I am certain the drives are degrading because they are SMR. Now I did what I probably should have done at the beginning - I bought two 2 TB WD RED Plus drives.

The plan:
I want to replace both Seagate drives with the WDs without loosing/moving the data. Currently the Pool is listed as Unhealthy with the problematic disk showing Self healed: 192512 (bytes?). As per this post I can just replace one disk at a time and resilver it in between. Could I also possibly add both WDs at the same time and then remove both Seagates? Could there be a problem with both drives being 2 TB with possible minor size differences? I plan to make a new pool on the Seagate drives for stuff I don't mind loosing.

 

[danb35]

Could I also possibly add both WDs at the same time and then remove both Seagates?

Sure, if you have the drive bays for it. Another thing you could do is add the two new disks as additional mirrors of the existing ones (making, temporarily, a four-way mirror), and once resilvering completes, detach the old ones.

 

[Etorix]

If you have two spare SATA ports (four total), you can just plug the new drives and replace the old drives by the new ones all in one go and without removing any drive, meaning you have full redundancy.

 

[Computer8080]

If you have two spare SATA ports (four total), you can just plug the new drives and replace the old drives by the new ones all in one go and without removing any drive, meaning you have full redundancy.

So just checking if I understand this correctly. I can just select Replace on both drives at the same time? Would this put more strain on the SMR drives?

 

[danb35]

I can just select Replace on both drives at the same time?

Correct.

Would this put more strain on the SMR drives?

I wouldn't expect so, given that they're mirrored.