ZFS health checker script from calomel.org, adapted for Ubuntu Linux

zfs_health.sh

#! /bin/sh
# ZFS health version for Ubuntu
# You must install the package "dateuils" from the univers
# 
# Based on Calomel.org
#     https://calomel.org/zfs_health_check_script.html
#     FreeBSD ZFS Health Check script
#     zfs_health.sh @ Version 0.16

# Check health of ZFS volumes and drives. On any faults send email.


# 99 problems but ZFS aint one
problems=0


# Health - Check if all zfs volumes are in good condition. We are looking for
# any keyword signifying a degraded or broken array.

condition=$(/sbin/zpool status | egrep -i '(DEGRADED|FAULTED|OFFLINE|UNAVAIL|REMOVED|FAIL|DESTROYED|corrupt|cannot|unrecover)')
if [ "${condition}" ]; then
        emailSubject="`hostname` - ZFS pool - HEALTH fault"
        problems=1
fi


# Capacity - Make sure the pool capacity is below 80% for best performance. The
# percentage really depends on how large your volume is. If you have a 128GB
# SSD then 80% is reasonable. If you have a 60TB raid-z2 array then you can
# probably set the warning closer to 95%.
#
# ZFS uses a copy-on-write scheme. The file system writes new data to
# sequential free blocks first and when the uberblock has been updated the new
# inode pointers become valid. This method is true only when the pool has
# enough free sequential blocks. If the pool is at capacity and space limited,
# ZFS will be have to randomly write blocks. This means ZFS can not create an
# optimal set of sequential writes and write performance is severely impacted.

maxCapacity=80

if [ ${problems} -eq 0 ]; then
   capacity=$(/sbin/zpool list -H -o capacity | cut -d'%' -f1)
   for line in ${capacity}
     do
       if [ $line -ge $maxCapacity ]; then
         emailSubject="`hostname` - ZFS pool - Capacity Exceeded"
         problems=1
       fi
     done
fi


# Errors - Check the columns for READ, WRITE and CKSUM (checksum) drive errors
# on all volumes and all drives using "zpool status". If any non-zero errors
# are reported an email will be sent out. You should then look to replace the
# faulty drive and run "zpool scrub" on the affected volume after resilvering.

if [ ${problems} -eq 0 ]; then
   errors=$(/sbin/zpool status | grep ONLINE | grep -v state | awk '{print $3 $4 $5}' | grep -v 000)
   if [ "${errors}" ]; then
        emailSubject="`hostname` - ZFS pool - Drive Errors"
        problems=1
   fi
fi


# Scrub Expired - Check if all volumes have been scrubbed in at least the last
# 8 days. The general guide is to scrub volumes on desktop quality drives once
# a week and volumes on enterprise class drives once a month. You can always
# use cron to schedual "zpool scrub" in off hours. We scrub our volumes every
# Sunday morning for example.
#
# Scrubbing traverses all the data in the pool once and verifies all blocks can
# be read. Scrubbing proceeds as fast as the devices allows, though the
# priority of any I/O remains below that of normal calls. This operation might
# negatively impact performance, but the file system will remain usable and
# responsive while scrubbing occurs. To initiate an explicit scrub, use the
# "zpool scrub" command.
#
if [ ${problems} -eq 0 ]; then
   currentDate=$(date +%s)
   zfsVolumes=$(/sbin/zpool list -H -o name)

  for volume in ${zfsVolumes}
   do
    if [ $(/sbin/zpool status $volume | egrep -c "none requested") -ge 1 ]; then
        echo "ERROR: You need to run \"zpool scrub $volume\" before this script can monitor the scrub expiration time."
        break
    fi
    if [ $(/sbin/zpool status $volume | egrep -c "scrub in progress|resilver") -ge 1 ]
    then
        break
    fi
    scrubRawDate=$(/sbin/zpool status $volume | grep scrub | awk '{print $15 $12 $13}')
    if dateutils.dtest  today --ge $(dateutils.dadd -i '%Y%b%d' ${scrubRawDate} +9d)
    then
        emailSubject="`hostname` - ZFS pool - Scrub Time Expired. Scrub Needed on Volume(s)"
        problems=1
       fi
   done
fi


# Email - On any problems send email with drive status information and
# capacities including a helpful subject line. Also use logger to write the
# email subject to the local logs. This is also the place you may want to put
# any other notifications like playing a sound file, beeping the internal 
# speaker, paging someone or updating Nagios or even BigBrother.

if [ "$problems" -ne 0 ]; then
  echo "$emailSubject \n\n\n `/sbin/zpool list` \n\n\n `/sbin/zpool status`" | /usr/bin/mail -s "$emailSubject" root@localhost
  logger $emailSubject
fi

### EOF ###

Hi, there's a small problem in this script, such that if the last operation was a completed resilver, the scrub agecheck is never performed:

zpool status <mypool>
  pool:  <mypool>
 state: ONLINE
  scan: resilvered <size> in <time> with 0 errors on Sat May 28 11:38:17 2016

The problem is this line
if [ $(/sbin/zpool status $volume | egrep -c "scrub in progress|resilver") -ge 1 ]; then
which probably means to cancel the scrub-check if a resilver is in progress, but it also cancles if it is done. The egrep should be more specific.

I'm testing this on ZFS on Linux