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Ward 12-06-2008 01:30 AM

Cloning my Time Machine HD before repairing it
I've been running Time Machine for nearly a year, accumulating 619 GB of backup files (about 22 million actual files).

When Time Machine reported errors attempting to backup a 160 GB external FW HD, I talked to Apple Support and was advised to run a Disk Utility Verify on Time Machine's HD, and then do a Repair, if needed. Verify hung with its progress bar at 50%, probably indicating there's directory corruption.

Before I hand Time Machine's HD over to DiskWarrior, it seemed like a good idea to first clone that HD with SuperDuper! Then if DiskWarrior messes up, I'll have an opportunity to try another approach. (DiskWarrior has always been a faithful friend, but this task may be beyond it's capabilities.)

At the beginning, SuperDuper! was copying from one eSATA drive to another at 65 MB/sec. At that speed, it looked like a 4 hour copy. As time passed, the copy speed dropped. At 6 hours and 30 minutes, the clone is half done, and the copy speed down to 13 MB/sec. So I'm probably looking at another 12 hours or more.

Is this slowdown to be expected with a large disk? Or is directory corruption making SuperDuper's job more difficult or impossible?

If the HD cloning fails or slows down to glacial speed, my next attempt will be let DiskWarrior create a new directory, and use SuperDuper! to clone DW's Preview of the repaired HD. Then I'll let DW write a repaired directory.

I welcome your comments and advice.

-- Ward

dnanian 12-06-2008 08:07 AM

It can take a very long time to complete the copy, due to the various hard link creations, etc. Having it slow down is entirely expected... as is having the status display pause, sometimes for quite a while. There's a lot going on when this is copied.

However, I'm not sure it's going to work, given that you have corruption. We'll see... but leave it until you get an error or success.

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