Thinning the Archive

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Level 2

194 points

Thinning the Archive

Hi All,

I've got Time Machine running right now on a 1.5TB external HD with about 900mb of Time Machine backups going back a year (I do audio so the files build up). I'm about to go on the road for about 10 months, and I would like to bring a physically smaller, bus powered hard drive. But there are no 1.5 TB bus powered drives. I currently have a 500gb portable drive that I could use for this purpose, or I could put in a 1TB disc into the enclosure if you think it makes a big difference.

My main computer has about 420gb of data on it between the system and data drive.

My question is how to best go about making the smaller drive my Time Machine backup. Should I simply reformat it and start anew, or is there a way to take some of the existing backup but not all of them? My oldest backup goes back a year.

Any advice would be appreciated.

PS -- I also use Dropbox for smaller documents (but not my audio file library or movies or anything), so I have some redundancy.

17" Macbook Pro 2007 2.4g C2D, 4G RAM, 750G HD + 180g SSD, Mac OS X (10.6.4), Peripherals include Dell monitor and USB hub, OWC 1.5T HD, Apogee Duet

Posted on Jul 24, 2010 5:42 PM

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Answer 1

thomas_r.

Level 7

32,031 points

Jul 24, 2010 5:56 PM in response to JES

My main computer has about 420gb of data on it between the system and data drive.

In that case, the 500 GB drive will not be large enough for TM backups... TM needs about 2-3 times more space on the backup drive than what is being backed up. You could either get a larger drive or you could use something like [Carbon Copy Cloner|http://www.bombich.com> to just do a straight clone, no incremental backups. (You could fit some incremental backup data with CCC if you chose.)

Of course, keep in mind that you should have a minimum of 2 separate backups... consider how important that will be to you while traveling for such a long time.

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Answer 2

Pondini

Level 8

38,863 points

Jul 24, 2010 6:08 PM in response to JES

JES wrote:
. . .
I could put in a 1TB disc into the enclosure

Yes, definitely. Then you can just copy your existing backups to it, per #18 in Time Machine - Frequently Asked Questions (or use the link in *User Tips* at the top of this forum).

My question is how to best go about making the smaller drive my Time Machine backup. Should I simply reformat it and start anew,

That's your second best bet. 😉

But a 500 GB drive is likely too small to back up 420 GB of data anyway. It varies greatly, of course, depending on how you use your Mac, but our "rule of thumb" here is that it should be 2-3 times the size of the data it's backing-up.

In fact, you may not be able to do an initial backup, since Time Machine adds 20% to the estimated size of each backup, and 420 GB * 1.2 = 504 GB. You'd have to exclude some things per #10 in Time Machine - Frequently Asked Questions (or use the link in *User Tips* at the top of this forum), run a backup, then remove the exclusions and run another.

or is there a way to take some of the existing backup but not all of them?

Not easily.

You can't copy some backups. You'd have to manually delete most of your backups (via Time Machine, not the Finder -- see #12 in the FAQ), until they're small enough to fit on the other drive, then copy the backups to it, per #18 in the FAQ. Both of those processes will take a very long time.

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