Time Machine and changing hard disk name problem

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Level 1

10 points

Time Machine and changing hard disk name problem

I have been using Time Machine happily for 2 years now. Four days ago I swapped my 320GB disk for a 400GB and did a Time Machine backup just before I cloned the original.
The original disk was called "320 GB" (original !) and I called the new disk "400 GB"......

Last night I went to do a Time Machine backup and I could see that it was going to be millions of items and about 60GB - the size of the full backup. Presumably because I have renamed the hard disk. I have now changed the disk name back to "320 GB" and again Time Machine wants to do a 60GB (full) backup.

What are my options - should I delete the .plist file and restart - will this lose the history of changes between the 10th and 14th October (when the 320 GB became 400 GB) and Time Machine will then have to compare the current disk (320 GB) with what is on the backup and only do an incremental backup ???

MacBook, Mac OS X (10.6.4)

Posted on Oct 14, 2010 9:14 AM

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Answer 1

Pondini

Level 8

38,863 points

Oct 14, 2010 9:32 AM in response to Tintin007

Tintin007 wrote:
. . .
Last night I went to do a Time Machine backup and I could see that it was going to be millions of items and about 60GB - the size of the full backup. Presumably because I have renamed the hard disk.

No, it's because it's a new drive. Time Machine keeps track of drives by their UUIDs, not names. (And this happens even if you do a full restore to the original HD: http://support.apple.com/kb/TS1338)

And no, there's no known way to fool it into thinking the new drive is really the old one. It will do a new, full backup, and perhaps need to delete a lot of old backups to make room.

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Answer 2

k.panic

Level 3

605 points

Oct 14, 2010 9:38 AM in response to Pondini

Actually there may be a UUID workaround, but whether or not it's worth it is up to you.

A quick google found this:

PLEASE NOTE: This article shows the workaround under the assumption the UUID of your INTERNAL drive has changed, not your external. It may be entirely possible to adapt the script to your needs, but here's the heads up anyway.

http://simon.heimlicher.com/hints/macosx/time-machine-volume-uuid

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Answer 3

Tintin007 Author

Level 1

10 points

Oct 14, 2010 10:17 AM in response to k.panic

Many thanks - I did not realise that the UUID referred to the drive....

That explains why there is no problem when you move to a new Mac and use the same (physical) hard disk in the new machine...

So I might as well change the disk name back to "400 GB" and I will try my luck with the script - it won't need adapting since it is only the drive that has changed (and the name)......

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Answer 4

Pondini

Level 8

38,863 points

Oct 14, 2010 10:30 AM in response to Tintin007

Tintin007 wrote:
Many thanks - I did not realise that the UUID referred to the drive....

That explains why there is no problem when you move to a new Mac and use the same (physical) hard disk in the new machine...

Time Machine will do a full backup of a new Mac.

So I might as well change the disk name back to "400 GB"

For convenience, you might want to give it a slightly different name. When you're looking at your backups, the two drives will be shown separately. If you enter Time Machine while looking at one, you won't be able to see the backups for the other one. If you enter Time Machine while looking at your Computer, as in the sample below, you'll see two different names in the center part of the window, on different backups. If the names are a bit different, it will be more obvious which is which:
|

|

See #E3 in [Time Machine - Troubleshooting|http://web.me.com/pondini/Time_Machine/Troubleshooting.html] (or use the link in *User Tips* at the top of this forum).

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Answer 5

Tintin007 Author

Level 1

10 points

Oct 14, 2010 12:18 PM in response to Pondini

Thanks again - at the moment the hard disk is called 320 GB and I will leave it at that.

I have turned off Time Machine but can browse and "quick-look" files from last year without doing anything unusual......

I will try the script and a backup and report back tomorrow

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Answer 6

Tintin007 Author

Level 1

10 points

Oct 22, 2010 3:43 AM in response to Tintin007

Ok - TM still wants to backup 60GB (full backup).

The script does not work under Snow Leopard ⚠ there are some Terminal commands dropped from Leopard.

I know the UUID of the old disc and I know the UUID of the new disk. Surely it should be simple enough to trick Time Machine into thinking that the existing backups are linked to the new UUID ??

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Answer 7

k.panic

Level 3

605 points

Oct 25, 2010 5:59 AM in response to Tintin007

Yikes.

Yeah, I've had mine do that a few times, usually I just let it go. I've not managed to switch/force TM to like the UUID mismatch, but I know there are some that have, thought I'd at least try and point you in that direction.

If you have plenty of room on your backup destination, I wouldn't worry too much about it if it only happens once.

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