July 16, 20232 yr Not really a problem as such, but I've just set up a new ZFS pool to try out some of these new features I've heard so much about, and I had a bit of a pleasant surprise. 3 x 2TB SSDs, running RAID-Z, so I had assumed that it would give me a total pool capacity of around 3TB. But it's actually 3.9TB total? Just wondering how the pool could cope with the loss of one drive, with two "copies" of everything, when the total disk space is only 6TB, not 7.8TB...
July 16, 20232 yr Solution Raidz uses a portion on each disk for parity. So a bit under 4 TB is about what's expected. You lose the capacity of a whole disk with raidz1 and you lose the capacity of 2 disk with raidz2.
July 17, 20232 yr Author Riiight, gotcha - conceptually parity works more like it does in the Unraid array (but striped across all disks) rather than the "two copies" version I had in my head. Thanks for clearing up.
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