I'm building a RAIDZ2 ZFS system, using Ubuntu 13.10 as a base system, and zfsonlinux's packages, having 6 disks dedicated to the pool data and a couple of SSD partitions to do ZIL log and L2ARC cache. My HDDs are all 2.0 TiB (in fact: slightly less than 2.0 TiB) drives.
Yet, once the pool was created,
zpool list unexpectedly reports a pool having 10.9 TiB size, 1.93 MiB allocated, and 10.9 TiB free. How is it getting nearly 11 TiB free in a RAIDZ2 having a total of 12.0 TiB of disks? I was expecting to have a mere 8.0 TiB of free space (4.0 TiB being allocated to parity).
Oh, this is apparently a very similar question to ZRAID1 pool size bigger than expected, but about RAIDZ2 instead of RAIDZ... I'll post this anyway, in case anyone cares about RAIDZ2 for their searches.