ZFS Health Check Script

zfs_health.sh

#! /usr/local/bin/bash
#
# Calomel.org 
#     https://calomel.org/zfs_health_check_script.html
#     FreeBSD 9.1 ZFS Health Check script 
#     zfs_health.sh @ Version 0.15

# Check health of ZFS volumes and drives. On any faults send email. In FreeBSD
# 10 there is supposed to be a ZFSd daemon to monitor the health of the ZFS
# pools. For now, in FreeBSD 9, we will make our own checks and run this script
# through cron a few times a day.

# Changelog
# Peter van der Does - Always send an email, even if there is no problem.
#                      I prefer to know a script has run even when there is no problem.
# June 24, 2015
# Peter van der Does - When a scrub is needed the email subject line only has to inform us once.

# 99 problems but ZFS ain't one
problems=0
emailSubject="`hostname` - ZFS pool - HEALTH check"
emailMessage=""

# 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="$emailSubject - fault"
  problems=1
fi


# Capacity - Make sure pool capacities are 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)
  for line in ${capacity//%/}
  do
    if [ $line -ge $maxCapacity ]; then
      emailSubject="$emailSubject - 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="$emailSubject - 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 schedule "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.
#
# The scrubExpire variable is in seconds. So for 8 days we calculate 8 days
# times 24 hours times 3600 seconds to equal 691200 seconds. 

scrubExpire=691200

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

    ### FreeBSD with *nix supported date format
    scrubRawDate=$(/sbin/zpool status $volume | grep scrub | awk '{print $15 $12 $13}')
    scrubDate=$(date -j -f '%Y%b%e-%H%M%S' $scrubRawDate'-000000' +%s)

    ### Ubuntu with GNU supported date format
    #scrubRawDate=$(/sbin/zpool status $volume | grep scrub | awk '{print $11" "$12" " $13" " $14" "$15}')
    #scrubDate=$(date -d "$scrubRawDate" +%s)

    if [ $(($currentDate - $scrubDate)) -ge $scrubExpire ]; then
      if [ ${problems} -eq 0 ]; then
        emailSubject="$emailSubject - Scrub Time Expired. Scrub Needed on Volume(s)"
      fi
      problems=1
      emailMessage="${emailMessage}Pool: $volume needs scrub \n"
    fi
  done
fi


# Notifications - On any problems send email with drive status information and
# capacities including a helpful subject line to root. Also use logger to write
# the email subject to the local logs. This is the place you may want to put
# any other notifications like:
#
# + Update an anonymous twitter account with your ZFS status (https://twitter.com/zfsmonitor)
# + Playing a sound file or beep the internal speaker
# + Update Nagios, Cacti, Zabbix, Munin or even BigBrother

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

### EOF ###

Thanks for the script, had to remove -i from https://gist.github.com/petervanderdoes/bd6660302404ed5b094d#file-zfs_health-sh-L27 to avoid old zfs version being reported as unhealthy (Some supported features are not enabled on the pool. The pool can still be used, but some features are unavailable.).

The date parsing on Ubuntu is unreliable if you mix pools which take more than one day to scrub with pools that don't, or if you have pools which sometimes (but not always) take more than one day to scrub. This is because the zpool status command will selectively include or omit the X days tokens, throwing off the counts used in the awk command that follows.

We can make this a little more robust by having awk parse from the end going backwards, rather than from the front going forwards:
scrubRawDate=$(/sbin/zpool status $volume | grep scrub | awk '{print $(NF-4)" "$(NF-3)" " $(NF-2)" " $(NF-1)" "$(NF)}')