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You are here: MacNN Forums > Software - Troubleshooting and Discussion > macOS > How do you swap your main disk without Time Machine noticing?

How do you swap your main disk without Time Machine noticing?
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Simon
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Jan 13, 2009, 05:27 PM
 
So a friend of mine here at work came to me with a Time Machine problem. She had swapped her internal disk and couldn't get TM to resume her backups.

Originally, she had booted from the install DVD and used Disk Utility to clone her old internal drive onto a new drive. She then swapped the old internal with the new drive and booted from the new drive. That all worked just fine. The problems started when she ran TM. After preparing the backup for ages and deleting all the older backups TM bailed out with a warning that there wasn't enough space on the backup partition for a backup. Obviously TM was trying to backup the new drive next to the old backups instead of updating the old backups. And since the backup partition wasn't twice as large as the data my friend has it didn't succeed.

So therefore my question, how should she have swapped the drives so that TM wouldn't have noticed? Or how should she have handled TM so that it would update the old backups as if nothing had happened instead of trying to start a new backup next to the old one?
     
Spheric Harlot
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Jan 13, 2009, 05:38 PM
 
1. Swap drives internal drives physically.
2. From Leopard install CD, select "restore from Time Machine backup".
3. There is no step 3.
     
Hal Itosis
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Jan 13, 2009, 07:09 PM
 
Originally Posted by Simon View Post
So therefore my question, how should she have swapped the drives so that TM wouldn't have noticed? Or how should she have handled TM so that it would update the old backups as if nothing had happened instead of trying to start a new backup next to the old one?
According to this article > "Move Time Machine Backups to a New Volume" <
the requisite steps are:

1. Turn off Time Machine by telling it to stop using the original target for backups.
2. Turn off Spotlight indexing on that same Time Machine target drive.
3. Perform a *Block Copy* of the original Time Machine drive to the new disk.

(you'll be pleased to read that the author had trouble with CCC, and therefore recommends DU. )

Finally -- after the swap -- turn all the stuff back on.

[i've never actually done this, so... just passing it along untested.]

--

Whoops, actually that's for swapping out the Time Machine disk.
Well, the idea is similar... only copying different disks in her case. I think the
principles there (turn off TM, turn off Spotlight, do block copy) would still apply.
( Last edited by Hal Itosis; Jan 13, 2009 at 07:21 PM. )
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Simon  (op)
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Jan 14, 2009, 03:46 AM
 
Originally Posted by Spheric Harlot View Post
1. Swap drives internal drives physically.
2. From Leopard install CD, select "restore from Time Machine backup".
3. There is no step 3.
That works. Unfortunately block copies are just so much faster than MA.
     
Simon  (op)
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Jan 14, 2009, 03:47 AM
 
Originally Posted by Hal Itosis View Post
Whoops, actually that's for swapping out the Time Machine disk.
Well, the idea is similar... only copying different disks in her case. I think the
principles there (turn off TM, turn off Spotlight, do block copy) would still apply.
Interesting. So shutting off TM and Spotlight on the old drive before doing the block copy and swap should be sufficient?

Has anybody here done this before?
     
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Jan 14, 2009, 04:02 AM
 
Apple should make that process much easier.

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Spheric Harlot
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Jan 14, 2009, 06:55 AM
 
Originally Posted by Simon View Post
That works. Unfortunately block copies are just so much faster than MA.
This has nothing to do with Migration Assistant.

Restoring a full system from a Time Machine backup took less than forty-five minutes, INCLUDING install, on an alu iMac using Ethernet from a Time Capsule, last time I tried it.

There is no information to analyze, no dates to compare - all that is already done before the actual backup is even created. Restoring is extremely fast.
     
OreoCookie
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Jan 14, 2009, 07:04 AM
 
Originally Posted by Simon View Post
That works. Unfortunately block copies are just so much faster than MA.
Depending on your interface, a Time Machine restore/migration from an external drive takes about 45 minutes to 2 hours. In many cases, the transfer rate is limited by the interface (in my case, it was limited by the transfer rate of USB) and not the harddrive. Since it's a one-time-deal that requires zero fiddling afterwards, it actually saves time if you do it that way.

Regarding the original question: Time Machine analyzes the name of the volume and the ID of the harddrive. In case of my parents' new Mac mini, it has sufficed to rename the new harddrive and use the exact same volume name (cases of letters matter here!).
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Simon  (op)
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Jan 14, 2009, 08:25 AM
 
Originally Posted by Spheric Harlot View Post
This has nothing to do with Migration Assistant.
Well AFAIK restoring from TM uses the same underlying framework as MA uses to restore form a TM backup. If you open MA you will see one of the options is to restore from a TM backup.

But that's all really not important. The point I was trying to make is that this is a file copy. If I have two fast drives connected to SATA a block copy is going to be at least 50% faster than a file copy. There is no interface bottleneck (the advantage of SATA vs. USB/FW bridges)

Restoring a full system from a Time Machine backup took less than forty-five minutes, INCLUDING install, on an alu iMac using Ethernet from a Time Capsule, last time I tried it.
Sure, I don't doubt that. But with the amount of data she has on that disk (the 10GB system install is negligible compared to the 600 GB apps and files) you are looking at roughly 4h vs. 2h. Why should she not save 2h i it's as easy as quickly switching TM and Spotlight off and turning them back on once you're done.
     
Spheric Harlot
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Jan 14, 2009, 08:27 AM
 
Originally Posted by OreoCookie View Post
Regarding the original question: Time Machine analyzes the name of the volume and the ID of the harddrive. In case of my parents' new Mac mini, it has sufficed to rename the new harddrive and use the exact same volume name (cases of letters matter here!).
It's more than that.

I recently had to get my MacBook repaired and chucked my internal drive into a rental replacement during that time.

Time Machine refused to recognize the previous backup and insisted on creating a new one, even though volume name and even machine name were identical (Time Machine named the backup "blackjack 2"; the original was "blackjack"). Once I got the MacBook back and swapped the drives back, Time Machine recognized the old backup and told me it'd been six weeks since my last backup.
     
Simon  (op)
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Jan 14, 2009, 08:27 AM
 
Originally Posted by OreoCookie View Post
Regarding the original question: Time Machine analyzes the name of the volume and the ID of the harddrive. In case of my parents' new Mac mini, it has sufficed to rename the new harddrive and use the exact same volume name (cases of letters matter here!).
You see that's what surprised me. The name of the HDD is exactly the same after the block copy. Obviously TM looks at more than just the partition name. But if switching TM off and on before and after cloning works, I'd say we have a winner.
     
Simon  (op)
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Jan 14, 2009, 08:31 AM
 
Originally Posted by Spheric Harlot View Post
It's more than that.
...
So you can confirm the solution Hal proposed definitely doesn't work?
     
OreoCookie
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Jan 14, 2009, 08:47 AM
 
It worked for my parents before, too, but it did not resume the old backups, it started a new one. We got back to the old backup series by renaming it. Since I had to do this only twice, I don't know what other steps to take (other than to restore from Time Machine). Just to make sure, with harddrive ID, I really mean the numerical ID of that specific drive, not the name of the volume.
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Spheric Harlot
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Jan 14, 2009, 08:50 AM
 
Originally Posted by OreoCookie View Post
It worked for my parents before, too, but it did not resume the old backups, it started a new one. We got back to the old backup series by renaming it. Since I had to do this only twice, I don't know what other steps to take (other than to restore from Time Machine). Just to make sure, with harddrive ID, I really mean the numerical ID of that specific drive, not the name of the volume.
I took the actual drive and removed it from the MacBook, and then stuck the actual drive into a different MacBook, and Time Machine had to create a new backup.
     
Spheric Harlot
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Jan 14, 2009, 08:52 AM
 
Originally Posted by Simon View Post
So you can confirm the solution Hal proposed definitely doesn't work?


Huh? What does replacing the Time Machine backup drive have to do with what I described?
     
OreoCookie
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Jan 14, 2009, 09:24 AM
 
Originally Posted by Spheric Harlot View Post
I took the actual drive and removed it from the MacBook, and then stuck the actual drive into a different MacBook, and Time Machine had to create a new backup.
That's a different situation: the machine's ID also enters into the equation, I forgot to mention that. If I remember correctly, the machine's ID enters the directory structure even (cannot check that at the moment, my Time Machine drive is at home).
( Last edited by OreoCookie; Jan 14, 2009 at 09:31 AM. )
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Spheric Harlot
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Jan 14, 2009, 11:11 AM
 
Originally Posted by OreoCookie View Post
If I remember correctly, the machine's ID enters the directory structure even (cannot check that at the moment, my Time Machine drive is at home).
Definitely not.

The backup directories have timestamped names; that's all.
     
Hal Itosis
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Jan 14, 2009, 01:40 PM
 
Originally Posted by OreoCookie View Post
It worked for my parents before, too, but it did not resume the old backups, it started a new one. We got back to the old backup series by renaming it. Since I had to do this only twice, I don't know what other steps to take (other than to restore from Time Machine). Just to make sure, with harddrive ID, I really mean the numerical ID of that specific drive, not the name of the volume.
There are a couple of hidden files that TM uses to match up source to target.
I pretty much thought it took a logic board swap to mess that up though...
not just a new HD.

We can see some of them like so:

$ ls -l /var/db/.TimeMachine.Cookie /Volumes/*/.0*
-r-------- 1 root wheel 16 Dec 31 2007 /Volumes/L_d100g/.001a2b3c4d5e
-r-------- 1 root wheel 16 Dec 31 2007 /var/db/.TimeMachine.Cookie

That ".001a2b3c4d5e" should match the en0 hardware address of the source Mac.
Assuming only two files are found above, we can test if they match with:

$ sudo diff /var/db/.TimeMachine.Cookie /Volumes/*/.0*
[should get no output if they do]

More info here:
Repair Time Machine after logic board changes
New Logic Board? Time Machine Thinks "New Computer!"

--

I wouldn't think just an HD change out would call for all that, but i've never done any of this stuff myself.
-HI-
     
CharlesS
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Jan 14, 2009, 02:03 PM
 
Originally Posted by Spheric Harlot View Post
It's more than that.

I recently had to get my MacBook repaired and chucked my internal drive into a rental replacement during that time.

Time Machine refused to recognize the previous backup and insisted on creating a new one, even though volume name and even machine name were identical (Time Machine named the backup "blackjack 2"; the original was "blackjack"). Once I got the MacBook back and swapped the drives back, Time Machine recognized the old backup and told me it'd been six weeks since my last backup.
That's because Time Machine does keep track of your computer's MAC address (although you can work around that). I had to do that after I got the logic board in my MBP replaced. If you just put a new hard drive in your existing Mac, though, your MAC address hasn't changed, and this doesn't apply.

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Simon  (op)
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Jan 14, 2009, 02:45 PM
 
So why then would TM notice a change if you take a new hard drive an put it into the same Mac? Keep in mind in this case the new HD was a block-copied clone of the old one so there should be absolutely no differences in terms of the content.

The only explanation I can think of is that TM does indeed look at something like the drive ID. And if that is actually the case, the only way to do this seems to be through the restore method. Which kind of stinks because it's comparably slow.
     
Simon  (op)
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Aug 18, 2009, 05:13 AM
 
Any ideas if these procedures have changed with Snow Leopard's TM?

Swapping a TM disk with Disk Utility cloning is easy enough (link, link).

OTOH swapping the computer and retaining the TM disk and contents (like for example after a motherboard exchange) is doable (link, link), but it's a major PITA.

Has anybody heard if Apple has made this easier in SL's updated Time Machine?
     
   
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