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mschmitt
05-10-2009, 05:40 PM
Some comments on SuperDuper's impact on root folder creation dates, and the consequences to running DiskWarrior. I saw some older messages in the forum, but they were running in Erase mode, not Smart Update...


I'm running SuperDuper! in Smart Update mode to an external drive that also contains a Time Machine database.

A few days ago I ran DiskWarrior 4.1.1 against that drive. The result was it needed to repair the creation date on 958,390 hard link files! I believe that represents every single hard link on the drive.

Alsoft says it did this because it had to repair the root folder creation date. Repairing this date then caused it to need to repair all the hard link directory entries -- the hard link catalog entry's creation date should be the same as the root folder, or the HFS+ private data folder.

It got this way because every time I run SuperDuper (even with Smart Update), it changes the backup drive's root folder creation date to match the source drive. The result is that the root folder creation date is less than the volume header creation date.

Now the question is, will this be a constant repair cycle? The old Time Machine hard links have already been repaired, so they won't need to be fixed again, even after DW repairs the root date.

If I manually create a hard link on the backup volume, it gets created with whatever the current root date is, so if it is after a SD clone, that link will get repaired by DW.

I haven't figured out whether Time Machine will create new "bad" hard links. It doesn't seem to, but I don't know why not. Maybe I'm not looking in the right place.

The other case would be if a SuperDuper creates a new hard link on the destination drive, because it now exists on the source drive. I don't know what it is going to do in this case.

dnanian
05-10-2009, 06:06 PM
We've discussed this with Alsoft in the past, and they've indicated that this difference doesn't really matter at all. (Using conventional hard link APIs, we can't actually set a hard link creation date...)

mschmitt
05-10-2009, 06:30 PM
I guess I was wondering if it is correct for SuperDuper! to modify the destination's root folder creation date, especially to be less than the volume header creation date.

Also, there is the question of if DiskWarrior has changed its behavior to support Time Machine and directory hard links. What it considered valid in the past may not be what it does today.

Alsoft told me that after it repaired the million hard links, the Time Machine database would be corrupt:

"If the root creation date is damaged, there wouldn't be a retrievable
backup, even if Time Machine is still making a backup of files. The
information needs to be repaired."

dnanian
05-10-2009, 06:41 PM
Well, I can say quite definitively that the difference does not make Time Machine's backups invalid. I've tested this myself hundreds of times.

As far as copying the root creation date goes, we're copying the contents of the volume, not the volume's structure. So copying all the aspects of those files and folders is appropriate, as far as I'm concerned...