ZFS periodic scrub script

I have 4 ZFS / Sun fire x4540, I do 4 times scrub for one ZFS a year. Here is my script

#!/bin/bash
###############################################################################
# FILE:         zfs_scrub.sh
# PURPOSE:      run scrub on each zfs pool every four months
#
# DATE:         Sep. 2010
#
#
# USAGE:        zfs_scrub.sh
#
# CHANGES:
# NOTES:
#
###############################################################################

thishost=`hostname`

typeset -i h
dayofmonth=`date +%d`
monofyear=`date +%m`

suffix=`expr $monofyear % 4`
if [ $suffix == 0 ] ;then
  suffix=4
fi

zfspoolname="${thishost}_"$suffix

#  The following comments come from scrub description in zpool command
#         Begins a scrub. The  scrub  examines  all  data  in  the
#         specified  pools  to verify that it checksums correctly.
#         For replicated (mirror or raidz) devices, ZFS  automati-
#         cally  repairs  any  damage discovered during the scrub.
#         The "zpool status" command reports the progress  of  the
#         scrub  and summarizes the results of the scrub upon com-
#         pletion.
#
#         Scrubbing and resilvering are very  similar  operations.
#         The  difference  is  that resilvering only examines data
#         that ZFS knows to be out  of  date  (for  example,  when
#         attaching  a  new  device  to  a  mirror or replacing an
#         existing device), whereas scrubbing examines all data to
#         discover  silent  errors  due to hardware faults or disk
#         failure.
#
#         Because  scrubbing  and  resilvering  are  I/O-intensive
#         operations, ZFS only allows one at a time. If a scrub is
#         already in progress,  the  "zpool  scrub"  command  ter-
#         minates  it  and starts a new scrub. If a resilver is in
#         progress, ZFS does not allow a scrub to be started until
#         the resilver completes.
#         -s    Stop scrubbing.

## At here, check if the pool is at good state before run scrub.

pool_status=`/usr/sbin/zpool status $zfspoolname | grep state | awk '{print $2}'`
#echo $pool_status
if [ "$pool_status" == "ONLINE" ] ; then
  #echo "run scrub"
  /usr/sbin/zpool scrub $zfspoolname
fi
exit 0