I created a 59.7TB Pool with 8x RAIDZ2, 8x RAIDZ2, 6x RAIDZ2, 2x Spare (3TB HD) The pool shows up at 59.7TB. This is exactly what I expected. Then I go to create a ZFS Folder and it says I only have 41.1TB available. Whats going on? The link below is a screenshot of the ZFS Folder creation in Napp-IT.


Side question, these are the speeds I'm getting. Is this good? Should I be doing something to optimize it? 20.48 GB in 70s = 292.57 MB/s Write 20.48 GB in 30.5s = 671.48 MB/s Read



zpool list returns


backup 59.8T 147G 59.6T - 0% 1.00x ONLINE -

rpool 74G 3.42G 70.6G - 4% 1.00x ONLINE -

  • 1
    What is the output of zpool list? Also, from your description I gather you have 16 3TB disks of usable space; if you convert from disk manufacturers' TB's (1000^4 bytes) to regular TB's (1024^4 bytes) you have to multiply by a factor of roughly .91, which brings the pool's usable size to something like 43.7 TB.
    – pino42
    Nov 7, 2012 at 1:33
  • added zpool list to initial question. Nov 7, 2012 at 18:30

1 Answer 1


OK, it's clear now.

That happens because zpool list reports the total size and free space of all your storage space, without taking into account that you asked for redundancy. In fact, 22*3*1000^4/1024^4 amounts to 60.0, which sounds close enough to 59.8 (I don't know the exact size of the 3 TB disks).

On the contrary, zfs list (and the screenshot you linked) report the available space after taking redundancy into account.

For a few examples, look at this FAQ: Why doesn't the space that is reported by the zpool list command and the zfs list command match?


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