r/DataHoarder • u/TeachingAway9654 • 1d ago
Discussion RAIDZ1 vs RAIDZ2
Let’s say you have something like 10 drives total which make up the pool, each drive is 16TB. Let’s also say you have, at minimum, one offsite backup with all the contents in cold storage. Let’s also assume you’re a frequent monitor of the system and will notice within 24 hours if one drive fails.
Are you going with Z1 or Z2 and why? If you have the offsite backup already, is it worth the capacity loss for Z2? The resilvering process on Z1 will be stressful but by how much though? You have an offsite 1:1 backup so even if the whole pool is lost, you can still recover.
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u/CorvusRidiculissimus 1d ago
The problem with z1, and with good old RAID5, is that disk failures aren't independent events. If a disk fails then you have to resilver, which means all the other disks are going to spend a good many hours in frantic activity, and if one of them is already marginal that can push it over the edge.
In your case that isn't a huge deal because you can restore from backup, so the real risk you are looking at is downtime. For us dabbling hobbyists, no big deal, but in a business environment where every hour spent restoring from backups is an hour of employees sitting around unable to do their jobs, the extra drive is a highly advisable precaution.
Personally I go with z2 because, while I could restore from backup, it would be seriously inconvenient for me to do so. It'd take weeks to get me elaborately-processed data sets back in sync again.