App/Script for Unmounting a Drive?

Question

Does anyone have of know of a little executable file that you can place in your startup list that when Osx starts up will unmount a disk for you?
The reason that I ask is that I run OSx off an external RAID via tnunderbolt and do not use my imac internal drive at all. So to save wear and tear on that internal drive I would like to eject it as soon as OSx successfully loads on my RAID.
If OSx for some reason does not launch on my RAID then the script will never run and the internal imac HD with its OSx on will boot. This is exactly what I want.
Is there anyway that I can use automator to do this for me?
Can anyone help?
Steve

Answer 1

Here is a better version of my login unmount bash script:
#!/bin/sh
#disktool -e disk0s9
# example of change string.  This is change all.
# i=${diskName//" "/"\\ "}
# debug info
export PS4='+(${BASH_SOURCE}:${LINENO}):'
set -o xtrace
ls -l /Volumes
# list of disks to unmount.
disks=("classic" "Second 80" "Ext-80" "Macintosh-HD" "Ext 500")
for diskName in "${disks[@]}"; do
  echo "diskName =${diskName}="
# sometime it takes Mac OS X awhile to mount the disks.
# try four time to try to unmount each disk.
    for ((tryCount=0;tryCount<4;tryCount++))
    do
      diskutil unmount "/Volumes/${diskName}" | grep "Volume /Volumes/${diskName} unmounted"
      rc=$?
      echo "rc="$rc
      if [ $rc -eq 0 ]
      then
        echo "unmounted  i=${diskName} tryCount="$tryCount
        break
      fi
      echo "tryCount=${tryCount} when trying to unmount ${diskName}"
      sleep 8
    done
done