What is the best practice here when it’s safety first?
I was thinking
3 x 15 in Z3 but in case of a error that is 15 24TB drives that have to resilver
vs
4 x 11 in Z2 which would resilver considerable faster?
Actual RAID-Z2/3 width is:
- Your comfort level
- Amount of storage you want
- Time to make ZFS vDev whole again, (narrower widths resilver faster).
Some might consider 15 wide RAID-Z2/3 a bit too wide. But, not too far off from more common widths, like 10-12 disks.
With so many vDevs, a spare slot could be helpful. In general, replace in place is both faster and data safer, when the drive to be replace is still working. But, replace in place requires a disk slot, (data, power, cooling, and a place to put the disk).
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The cold/hot spare drive was also a consideration for me.
I was just wondering if there is a best practice on the resilver part vs Z2 or Z3
Or in other words, will a 15/Z3 wide be more susceptible to problems during resilvering that i might as well go with 11/Z2 wide.
DraidZ2 w spare ?
The point of draid is that it decreases resilver time by actually utilizing not spares.
The problem is that it’s an immutable configuration.
Depends really on your comfort level with drives failing. I chose a Z3 for my rig because I was very cautious. But given how infrequently drives do fail (w/SMART, scrubs, backups, and so on) a Z2 is likely perfectly OK, as long as you are around most of the time to take care of the issue. Z3 is likely best for locations where it might be a while for you to get to the problem, like a remote data center.
Me, I do not run hot spares because the system is local. Instead, I qualify my spare drives and set them aside. That preserves their life and lowers my electrical costs. Hot spares seem like another good idea for a remote system. However, having one spare drive bay in your rig is great for qualifying drives and for ensuring that a drive replacement is quick.
Lastly, I’d go with a 4x Z2 VDEV pool that is only 11 wide because the extra VDEV = extra IOPS vs a 3x Z3 VDEV pool (I’d expect 3+ GB/s throughout for large files) and resilvers will be quicker.
So if it was me, for a rig in my home, I’d go with 4x11 Z2.
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