If you have another Mac available to you, this is a fast way to boot up and get your recovery scan going. This method also provides the ability to verify the files immediately after they are recovered with the programs normally used to access the files.
To boot from a second Mac, you will be using what is referred to as FireWire or Thunderbolt Target Disk Mode. Additionally, you can use the secondary Mac as your workspace and to recover your files.
Turn off the machine with the hard drive you’d like to scan.
Connect both machines using a firewire or thunderbolt cable.
Boot the secondary Mac as you do normally.
Boot the machine with the drive you’d like to scan while holding the “T” key. Hold the “T” key until you see a FireWire or Thunderbolt icon floating across the screen.
On your secondary Mac install and launch Data Rescue.
On the source selection screen of Data Rescue, select the Target FireWire or Thunderbolt connected hard drive as the drive to scan and click ‘Next’.
On the Scan Type selection screen choose a scan method and press ‘Start’ to begin scanning for your files.