Restoring from a Time Machine Backup Took Four Days!

6 11 2007

Recently, a data corruption event occurred on my Intel iMac. The computer would not boot. Luckily, it had Leopard installed, and it was being fully backed up with Time Machine. So, I decided to do a full restore of the entire disk using the Time MAchine backup.

The iMac has a 120GB hard disk containing about 100GB of data. Time Machine was backing up to an external 500GB hard disk over USB 2. To do a full restore of the computer from a Time Machine backup, you start up the computer using your OS X install disk. There is a menu item to restore from a Time Machine backup. Simply choose which backup you wish to use, and it begins, doing the rest automatically.

The progress bar started calculating the time remaining to complete the backup, and in a few moments it indicated… 170 hours to complete! Progress bar time estimates typically start conservatively, and tone down to be more accurate after a little while. It did, a little – to about 100 hours. This seemed startling – You can copy a 100GB disk using Disk Utility or SuperDuper in a tiny fraction of that time. But, having the time and curiosity, I let it run. It indeed took over 100 hours to complete the restore of 100GB of data.

Holy cow! Almost four days to restore a system from a Time Machine backup! The restore was successful, but if this hour-per-gigabyte rate is typical, it is something that needs improvement right away!

So, has anyone else had occasion to do a full restore of this kind? Did it take an incredibly long time, or was my experience an exception?