Merging 2TM drives

[zoran]

I have my TimeMachine backup in two drives. I need one drive for other use, so i must stop using it for my TM backup. Searching inside its folders I've found that the two drives share backups of the same days. For example, both have a backup folder of the 5th of June 2015. This leads me to think that if i format the drive i want to release from Time Machine then the shared backup folders will be deleted and i probably will lose those backups!
What can i do? Is it possible to merge the backups of the drive i need with the backups of the second drive that is used by TimeMachine and if so, what do i do?

 

[zoran]

I guess this must be a hard case to solve, that's why i dont see any responses to it! On the other hand the title might not be very easy to understand... can a moderator please change the title of the thread to "Merging 2 TimeMachine drives"?

 

[Weaselboy]

I'm a bit confused what you are doing. So you have two separate drives and they each contain their own Time Machine backup? You are just alternating the drives between TM backup runs then?

If that is the case, both drives will contain a full backup of your drive and you can just stop using the second drive and erase it with no impact on the first drive.

 

[zoran]

No, im sorry, thats not the case! Perhaps i didn't explain it well, let me clear it out!
When i first got my iMac i was using a small drive (A) as my TM backup. Then after a few months i purchased a bigger drive (B) and decided to use that drive on the iMac as TMdrive. I never disconnected drive A, so they were both backing up data for TM.
Now i want to get rid of the first drive (A) but im afraid that data backup will be corrupted and i do not want that. Thats the reason why i was interested in merging them two drives and their backups!

 

[Weaselboy]

No, im sorry, thats not the case! Perhaps i didn't explain it well, let me clear it out!
When i first got my iMac i was using a small drive (A) as my TM backup. Then after a few months i purchased a bigger drive (B) and decided to use that drive on the iMac as TMdrive. I never disconnected drive A, so they were both backing up data for TM.
Now i want to get rid of the first drive (A) but im afraid that data backup will be corrupted and i do not want that. Thats the reason why i was interested in merging them two drives and their backups!

I think we are both talking about the same thing. If you have two drives connected and they are both being used as Time Machine backups, TM just alternates between one and the other. You could take either one and format it or even toss it in the trash and a full backup would still exist on the other drive.

 

[zoran]

Ok i understand what you say but those two drives didn't start backing up together. Drive B started backing up a few months after drive A had already begun!

 

[Weaselboy]

Ok i understand what you say but those two drives didn't start backing up together. Drive B started backing up a few months after drive A had already begun!

It won't matter. Drive B will still be a full backup.

All that would missing from B is old versions of files that were created then deleted before B existed.

Let's say you made a Word document in May and deleted it in June. A backed up version of that would still be on drive A assuming the drive never got full and Time Machine started purging off old data.

Then you added drive B to the mix in July. That Word document would not be in the archive of the B backup. But B would still contain a complete backup of everything on the drive from the time it was connected until now. Again, assuming it never got full and started purging old backups.

So as long as you know you don't need any old versions of deleted files from A, you can just erase it.

Does that help?

 

[zoran]

Thats what im afraid of... if i erase A then i will loose the files it has backed up in the beginning before B existed! Is that what you are saying?

 

[Weaselboy]

Thats what im afraid of... if i erase A then i will loose the files it has backed up in the beginning before B existed! Is that what you are saying?

You won't lose any files that are now on the Mac, you would only lose old versions or now deleted files that exist only in the A backup.

How about this... can't you just erase the B drive then copy the A drive to B, then that frees up A for you to use like you want. Are the respective drive sizes sufficient to allow that?

 

[zoran]

Yes i know that i will loose older files that were backed up on A a long time ago!
Regarding your proposal, i can't do that, drive A is 500GB, drive B is 3TB.

 

[Weaselboy]

Yes i know that i will loose older files that were backed up on A a long time ago!
Regarding your proposal, i can't do that, drive A is 500GB, drive B is 3TB.

If A is 500GB and B is 3TB (3,000GB), what can't you just erase B then clone A to B and toss A. That sounds like the end result you want yes?

 

[zoran]

Just by copying the files contained in drive A to drive B, recreates the TM backup directory? Is it that simple?

Also i think we got mixed up... let me say again... i want to keep the backupd files of the B drive but i want to add to it the files contained to drive A!

 

[Weaselboy]

Just by copying the files contained in drive A to drive B, recreates the TM backup directory? Is it that simple?

Also i think we got mixed up... let me say again... i want to keep the backupd files of the B drive but i want to add to it the files contained to drive A!

You don't want to just copy the files over. You want to clone the disk. You can do that with Disk Utility. First erase B to Mac OS Extended (Journaled) then go to the Restore tab and put A in source and B in destination and click restore. That will clone A to B.

If you have been continuously backing up with TM to both drives, there is no need to keep B. Everything on B will be on A, plus all the older versions from before B existed.

 

[zoran]

How can B be on A, A is only 50GB! Anyway, i take it you mixed up their names!

 

[Weaselboy]

How can B be on A, A is only 50GB! Anyway, i take it you mixed up their names!

No, I did not mix them up.

If in January you attached A and started backing up and continued to backup to that drive all along, then later on say in May added drive B and continued backing up to both all that time until now.... everything that is on B now would be on A.

Again I am assuming you kept both drives attached and let Time Machine complete full backups to both with nothing excluded.

 

[zoran]

But they are different sized, how can they have the same backup files in them? Unless you mean that A will not have as many older backups as B, but both will still have the same latest backup files in them? If that's not what your saying, im sorry i cant get it through my thick head

 

[simonsi]

How much space is used on each drive? By now A may have to delete older backups that were on A to make space, so B may actually have your oldest backup.

 

[Weaselboy]

But they are different sized, how can they have the same backup files in them? Unless you mean that A will not have as many older backups as B, but both will still have the same latest backup files in them? If that's not what your saying, im sorry i cant get it through my thick head

No... I am saying the opposite. A has been in use longer so it will have more "old" or versioned/deleted files on it than B. But they both will have a complete copy of the current or latest files on the drive.

Again, this is assuming both drives are not near full that would cause the TM system to begin purging old versions.