ZFS integrity during 2 disk resilver

[Flatbed0563]

Hi all,

 

I recently moved to zfs raidz2 for my main storage, the day after putting everything up again, I got 2 drives giving me smart warnings (current pending sector and offline uncorrectable error). I was planning on replacing the drives and resilver. However, I am wondering, how confident can I be about data integrity during the resilver. Can I be absolutely sure that if data gets corrupted due to a third drive failure, unraid will either correct or notify me?

[Kilrah]

Would only replace one at a time starting with the one in worse shape. If you replace both at the same time then no more correction is possible, and a 3rd drive failure would cause the loss of the entire pool.

Edited May 12 by Kilrah

[Flatbed0563]

Thx for the response.

Can I trust that each resilver will not corrupt any data, as the rebuild will calculate from a potentially faulty drive?

[Kilrah]

When you replace one drive there will be 2 sources of redundancy, so if one is unreadable it'll use the other. If both were bad the whole operation would fail AFAIK.

There are checksums so it can know if the data is correct or not. Either it rebuilds correct data or it can't and the pool is gone.

Edited May 12 by Kilrah

[Flatbed0563]

Thx for the info, that is actually a relief

[JorgeB]

Additionally, and if you have enough SATA ports to have all disks connected, you could do a manual replacement, so the old disks could still be read (except for the bad parts).