Comment by bensyverson
7 hours ago
The risk of z1 is that if you get a read error during resilvering, that data is permanently corrupted. The odds of this happening go way up the larger your individual drives are. This is why I chose RAIDZ2 for my NAS. I've had to resilver 2-3 times over the past 10 years, and never lost a byte of data.
Or like me where you get two SSDs in your pool that happen to likely be from the same batch and both decide to permanently disappear at roughly the same time :(
> The odds of this happening go way up the larger your individual drives are.
This is a common claim, but honestly, citation needed.
We can't just apply bit error rates from the datasheet that haven't been updated in 15 years. I'm sure a 2-day rebuild is a little more risky than a 4-hour rebuild, but I'm not convinced it's by all that much. Especially if you had a monthly scrub going to prevent disk rot and disks secretly getting super fragile.
> I've had to resilver 2-3 times over the past 10 years, and never lost a byte of data.
And how many times did you have a read error on one of your other disks during a resilver?
> The odds of this happening go way up the larger your individual drives are.
Technically true.
Practically? There are several other major factors - such as the quality of your drives, whether you periodically run zfs scrubs and/or disk read tests, and how long a resilver takes to complete.
Behind those are the eternal duo - size of budget and cost of failure.