Free space of 'zfs list' vs 'zpool list'

[Ludvig Strigeus]

I use zfs as root file system in a raidz1 configuration with 4x1.5TB disks.
zpool list says 150G available while zfs list says 47.1GB available. I do
not use any reservations but compression is enabled.

Due to the raidz with 4 disks, I would expect zfs list to say 150GB * 75% =
112.50GB free, not 47.1GB. Can someone explain where the 65GB have gone?

uname -a:
FreeBSD ludde.dyndns.org 8.2-RELEASE FreeBSD 8.2-RELEASE #0: Thu Feb 17
02:41:51 UTC 2011     root at mason.cse.buffalo.edu:/usr/obj/usr/src/sys/GENERIC
 amd64

zpool list:
NAME   SIZE   USED  AVAIL    CAP  HEALTH  ALTROOT
tank  5.44T  5.29T   150G    97%  ONLINE  -

zfs list:
NAME             USED  AVAIL  REFER  MOUNTPOINT
tank            3.96T  47.1G  28.4K  legacy
tank/data       3.95T  47.1G  3.95T  /data
... other file systems omitted ...

zfs list -t snapshot:
NAME                   USED  AVAIL  REFER  MOUNTPOINT
tank/data at 2011-08-05   385M      -  3.60T  -

zpool status:
        NAME                                            STATE     READ WRITE
CKSUM
        tank                                            ONLINE       0     0
    0
          raidz1                                        ONLINE       0     0
    0
            gptid/da8c85e1-f9fa-11de-a19c-001731eee65f  ONLINE       0     0
    0
            gptid/db86c6a9-f9fa-11de-a19c-001731eee65f  ONLINE       0     0
    0
            gptid/dc4efa95-f9fa-11de-a19c-001731eee65f  ONLINE       0     0
    0
            gptid/dcd40f4a-f9fa-11de-a19c-001731eee65f  ONLINE       0     0
    0

Thanks,
Ludde