Hey guys! I got my home lab setup going nicely now. One mirror vdev ZFS for my Nextcloud, granting very good performance! Small question though: I got two extra drives now and was thinking if it is worth it adding it already as extra mirror vdev. My question is the following:
Will resilvering of a single disk be quicker if I have my data striped over two mirror vdev than if all my data is in a single mirror vdev?
In other words, I was wondering in that sense if it is safer to replace a disk due to shorter resilver?
Are you doing this live or?
What do you mean live? Sorry, I’m still quite new to this…
No, not really. You’re going to want to read the TrueNas forum primers for ZFS and vdevs if you haven’t already. It’s critically important.
The data parity, error correction, and rebuild is within the zdev. If you lose a drive in the mirror, it’s rebuilt from the other drive in the mirror.
If you lost a disk in a z1 vdevs, it’s rebuilt from the other drives in the set.
A key concept of there is no parity and error correction during the period of a loss of a drive in a mirror or z1 until the resolver is complete. That’s why there’s z2/3/… Or you can create mirrors with more than two disks. Obviously some trades on capacity.
The rebuild speed is more about the drive size. Spinning drives can only write so fast, doesn’t matter how many other disks in the vdev. 4TB is long time, 12TB+ is eternity. SSD, much faster.
I wasn’t completely clear I think. I currently have 1*mirror vdev of 8TB. I’m thinking of adding another mirror vdev. That would stripe the data between both. Meaning that per vdev there would be less data. That would lead to quicker (thus safer?) resilversing in the case of a singular disk failure per vdev, correct?