The second hard disk will usually appear as a raw character device under /dev/rdsk. p0 is the entire drive, p1 is the first partition, p2 is the second etc.:
# fdisk /dev/rdsk/c0d1p0
Now that the second hard drive has been partitioned for use, create a second storage pool to keep separate from the syspool:
# zpool create datapool c0d1p0
Enable deduplication. This is why you installed Nexenta Core in the first place, yes?
# zfs set dedup=on datapool
Share the new storage pool. You may replace "*" with one or more hosts if you want to limit the access:
# share -F nfs -o rw=*,anon=0 /datapool
