augot Posted July 16, 2023 Share Posted July 16, 2023 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... Quote Link to comment
Solution david279 Posted July 16, 2023 Solution Share Posted July 16, 2023 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. Quote Link to comment
augot Posted July 17, 2023 Author Share Posted July 17, 2023 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. Quote Link to comment
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