ZFS backup script

#!/bin/sh
#to prep a new backup drive, insert into the drivecage, check logs for device, usually ada0 on my box, then
#zpool create backup ada0    if the drive is actually ada0


z=$1
b=$2

        if [ -z $b ]; then
                echo "Usage: $0 zpool_source_name backup_destination_name"
                exit 1
        fi

nd="${b}-$(date +"%F")"

test -z "$(zpool list -H | egrep -w "^${b}" | awk '{print $1}')" && zpool import $b 2>/dev/null
test -z "$(zpool list -H | egrep -w "^${b}" | awk '{print $1}')" && echo "Zpool \"${b}\" not found!" && exit 1


echo STARTED ON `date`
test -z "$(zfs list -H -t snapshot ${z}@${nd} 2>/dev/null | awk '{print $1}')" && zfs snapshot -r ${z}@${nd} || echo "Snapshot already exists."
od="$(zfs list -H -t snapshot -o name | egrep ^${z}@${b}- | tail -2 | head -1 | cut -d "@" -f 2)"


#Thanks Rob!
for i in `zfs list -H -r -o name $z | awk {'print $1'}`; do
  if [ `zfs list -r -H -t snapshot ${b} 2>/dev/null | awk '{print $1}' | grep -c "${i}\@"` -gt 0 ];then
    zfs send -v -i ${i}@${od} ${i}@${nd} | zfs recv -F ${b}/${i} 2>/dev/null
  else
    zfs send -v ${i}@${nd} | zfs recv -F ${b}/${i} 2>/dev/null
  fi
done

zfs list -H -t snapshot -o name | egrep ^${z}@${b}- | sort -r | tail -n +8 | xargs -n 1 zfs destroy -r
zfs list -H -t snapshot -o name | egrep ^${b}/${z}@${b}- | sort -r | tail -n +8 | xargs -n 1 zfs destroy -r

zpool export $b
echo FINISHED ON `date`