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jotaro 10-21-2007 02:19 PM

backup file size—SD vs. Time Machine
Here's another issue concerning backup, it seems to me:

SuperDuper duplicates what I am backing up, which means the backup file on the external hard drive will be about the same size as on my hard drive.

Time Machine, however, keeps adding to the backup hard drive. Let's say I made edits every day to a 2 GB movie file. Time Machine adds another 2 GB file to the backup disk every time I make an edit. If this is correct, the back up gets huge fast, far exceeding the size of my hard drive, which is 250 GB. Does this mean I should think about buying an external drive for Time Machine backup that is 3 or 4 times the size of my hard drive?? Does Time Machine recognize limits of back up disk and automatically lop off oldest files to make room for new ones?


dnanian 10-21-2007 03:12 PM

I'm sure Time Machine will "throw away" older copies of things to keep your data to the drive size. Realize, though, that the more space you give Time Machine, the more useful its style of copying will be.

jotaro 10-22-2007 02:26 AM

Well, yes, a giant hard drive would be ideal…at least hard drives are getting cheaper all the time. I think I saw a 1TB external hard drive for around $350. That ought to do the trick…for about 6 months.


Alex 02-09-2008 08:26 AM

OK, so now that SD 2.5 is out (yeah, cool, great! thanks) and can share a partition with time machine, what about the issue of having the TM size increasing everyday?
A time will come when SD won't have enough room left to do it's own backup.

Or would SD be able to remove the oldest TM backups as TM itself does?

Alex 02-09-2008 08:55 AM

Oh, I just saw the question as already been raised on this topic.

Papa Art 06-03-2009 04:31 PM

Another question
What might be the suggested partitions to set up on a 1.5TB external drive for use with both Time Machine and SuperDuper? (My internal hard drive is 1TB but with less than 200GB actually in use at this time.) Thank you!

dnanian 06-03-2009 04:33 PM

The big question is how large do you expect your internal to get? Data does tend to expand to fill the space you've got... :)

Papa Art 06-23-2009 02:33 AM

As it turns out (and as I learned via some experimentation since I didn't know how to answer your big question), your better response might have been something like "Don't worry about it -- the SD! and TM backups will co-exist just fine without any partitioning necessary."

I guess there is actually no reason for concern, at least until the entire 1.5TB drive is filled; and then TM will start deleting its oldest versions. But what will SD! do if there's not enough space to complete a smart update at that time? Thanks again!

dnanian 06-23-2009 07:09 AM

It will fail, as I explain in the FAQ: you're better off using separate partitions if you can.

Papa Art 06-23-2009 09:56 AM

Understood; it's just that I have no idea as to how to predict how large the data on the internal 1TB will eventually become. It seems as though either method (coexistence or partitioning) could require starting all over again at some point in the future.

dnanian 06-23-2009 10:00 AM

Clearly true, of course, if you don't have a full-size backup partition. Solution is to get a drive of sufficient size. :)

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