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.
> 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.
> 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?