Time Capsule Backup smaller than Hard Disk size

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Time Capsule Backup smaller than Hard Disk size

Hi,

I just got a new Time Capsule, 4th gen to backup my Mac. I have previously used a 1st gen Time Capsule without any issues and so I am wondering why my first back up with the new TC is smaller in size compared to my HD. The TC backup is about 294 GB and my HD is 319 GB in size -- a 25 GB difference. I read in other Apple Support Community discussions that a small discrepancy in size is not an issue, but I assume that 25 GB is a significant difference in size? I have nothing excluded from the Time Machine backup preferences.

Thank you for your help.

MacBook Pro, Mac OS X (10.7.2), Aperture 3.2.1

Posted on Feb 16, 2012 3:50 AM

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Answer 1

Feb 16, 2012 6:37 PM in response to Chau

Where are you getting HD usage from?? It is measured in different ways in different places.

Also look at Virtual Memory used in your Mac. The amount might surprise you.

see

http://support.apple.com/kb/HT1342

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Answer 2

Chau Author

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59 points

Feb 17, 2012 1:03 AM in response to LaPastenague

Hi LaPastenague,

Thank you for your reply. I am getting my HD usage info from clicking on my HD and pressing Apple/Command-i.

Thanks for the link, I checked my VM via Activity Monitor and it says that my VM size is 280 GB -- that seems a little weird (large) to me, but then again I probably just don't understand VM.

What further confuses me is that when I checked the TC preferences options section during the backup it told me that the "Estimated size of full Backup:" was 308.7 GB.

The estimated 308.7 GB did not match what TC seemed to be actually backing up (294 GB)... but does seem closer to what my actual HD size seems to be (319GB).

Thanks again for your help.

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Answer 3

Chau Author

Level 1

59 points

Feb 17, 2012 5:33 PM in response to LaPastenague

Hi,

Since my last reply, the backup completed and I noticed several bugs. When I enter TM, the time reported in the back up was not the actual time that it backed up my Mac, my TC which has a 2TB capacity was reported as having 1.7TB, and I got a few error messages... So I decided to do a zero out data erase and then reset the TC to factory settings. I also shut down and restarted my computer. Things seem to be better. The TC correctly reports itself as having a 2TB capacity and no error messages so far. However, I have a few questions:

(1) I renamed my TC base station with the same name from the previous attempt where I experienced errors. Will this effect my new attempt at backing up with TC and TM? Are there preferences and settings hidden that might make TM think it is backing up on the old TC base station? Should I have used a different name or does this not make a difference?

(2) TM seems to be backing up about 294GB once again and not the 308GB that I am expecting (the size of my HD after restarting the computer). There is a 14GB difference, is this significant? How can I find out what exactly is not being backed up onto TC by TM?

Thanks a lot for your much needed help and input.

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Answer 4

Feb 17, 2012 8:07 PM in response to Chau

(1) I renamed my TC base station with the same name from the previous attempt where I experienced errors. Will this effect my new attempt at backing up with TC and TM? Are there preferences and settings hidden that might make TM think it is backing up on the old TC base station? Should I have used a different name or does this not make a difference?

It won't make any difference.. TM will find no existing backup and will start again.

(2) TM seems to be backing up about 294GB once again and not the 308GB that I am expecting (the size of my HD after restarting the computer). There is a 14GB difference, is this significant? How can I find out what exactly is not being backed up onto TC by TM?

Thanks a lot for your much needed help and input.

I think you are still worrying about nothing.. if you want to do a backup which is more certain, do a disk image. You can do this with superduper, ccc, several other backup packages.. my favourite is clonezilla which uses a linux boot disk, but you might find it difficult to operate.

TM is not a disk clone. It is a file backup.. as such there are temp files which are not backed up.. there are also different ways of measuring files.. due to inefficiency of storage on a hard disk, a large number of small files will take up 20-50% more space than the actual file size.. the hard disk size will reflect used sectors not file bytes.. when a file is backed up, TM breaks it into small segments.. which fully occupy the sectors on the hard disk.. this added efficiency allows the backup to be smaller than the files on the drive.. don't worry it will rapidly get bigger than the hard disk.

Read how TM actually works.

http://pondini.org/TM/Works.html

It is rather different to what you imagine.

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Answer 5

Chau Author

Level 1

59 points

Feb 17, 2012 8:32 PM in response to LaPastenague

Hi LaPastenague,

Thanks for your reply and for confirming that the base station name makes no difference. As for question no. 2, okay I will assume that everything is fine and I will read through how TM actually works on Pondini's site. I guess I am making some wrong assumptions based on my experience with my first TC (1st gen) which seemed (if I recall correctly) to create a file backup that was similar in size to my HD size.

Thanks again.

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Answer 6

Dec 13, 2012 3:34 AM in response to Chau

I know this was a while back Chau, but thought I'd throw my 2 cents in (I also came across this while changing over TC's).

I had a ~600GB "backup" of my entire drive that only took about 230GB out of my TC - a HUGE discrepancy. I even manually backed up a few times to see if there was data that hadn't gone through the first time. If you go through and check all your 'document' folders though; Desktop, Movies, Photos etc .. their sizes should still equal what TC actually backed up. That's because your Mac has all those applications (as well as everything LaPastenague mentioned) that don't get backed up. I have Logic Pro for example (approx 200GB), and a few other space hungry apps which Time Machine doesn't backup locally to my TC. It's just the personal files and settings etc.

Just in case you were still wondering, hopefully that clears it up 😉

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Answer 7

Chau Author

Level 1

59 points

Dec 13, 2012 4:37 AM in response to michaelcharliehunter

Hi Michael,

Thanks for the reply -- yes a while back -- but I appreciate your clarifications nonetheless 🙂

Thanks again!

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Answer 8

Jan 21, 2013 9:45 AM in response to michaelcharliehunter

Michael, I have a similar situation to Chau, hence why I landed here. "Mac Basics: Time Machine" (http://support.apple.com/kb/HT1427) says that applications are indeed backed up -- "Time Machine automatically backs up your entire Mac, including system files, applications, accounts, preferences, email messages, music, photos, movies, and documents." I have a 60GB discrepancy on mine, which is worrying. Drilling in I found that the Cache for Album Artwork in iTunes folder was not backed up - and that's OK, but that's only a couple hundred MBs. I still haven't figured it out. Why do you think that your Time Machine singles out Logic Pro not to be backed up? Thanks!

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Answer 9

Jan 21, 2013 7:58 PM in response to Sergio727

Yeah I've since found out that all is indeed backed up Sergio (going into Migration Assistant shows the various things you can restore from backup).. I just assumed it was only personal files, but since that's not the case, I wouldn't have a clue..

I haven't had an issue with things missing from backup (so far).. So I guess it's the case of not fixing something if it isn't technically broke. Might mention it to a genius the next time I'm at a store ;)

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Answer 10

Chau Author

Level 1

59 points

Jan 21, 2013 8:32 PM in response to Sergio727

Hi Sergio, I would check out LaPastenague's Feb 17 and Feb 18, 2012 posts. TM seems to back up more efficiently and in a different way then we might think. There's also a helpful link to learn about TM that LaPastenague gave: http://pondini.org/TM/Works.html. Like Michael my TM works fine so I guess everything is okay despite some original size discrepancies.

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Answer 11

Jan 22, 2013 1:20 AM in response to Chau

Hi Michael, Hi Chau, thanks for your replies and the link. Actually, I think I might have found the discrepancy. I checked each "high level" folder (Downloads, Documents, etc), some of which showed minor variations but no 60GB. Finally, with invisible files unhidden, I found "MobileBackups", with a size of ~60GB. Indeed, there's a lot more info on this on the website LaPastenague had point to, specifically http://pondini.org/TM/30.html - Again, thanks all for your help on this!

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