time machine huge backup size

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time machine huge backup size

My brand new Time Machine backups are way larger than the drive size on some of my computers. I have a 500GB drive which, when backed up, it is coming out at 900GB. I have another brand new backup of a 250GB drive that is coming out at almost 500GB. I have 3 other machines backing up to the exact same Time Capsule drive, and they are roughly the correct size for the drive content that is on the associated computer and were started months ago. How can the first time brand new backup of a drive be twice the size (approx) of the drive itself? I thought at first there might have been aliases to other content and perhaps it copied that content, but my 250GB drive has no aliases to other data. The problem has only just occurred, and previous backups since the introduction of Time Capsule and Time Machine many years ago have been perfect. I have tried deleting the backup and starting again, but the result is the same for just two of my 5 macs. All my macs are on the same OS. The issue started a month or so back.

Posted on Oct 31, 2016 12:57 PM

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Answer 1

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Camelot

Level 9

56,955 points

Oct 31, 2016 1:03 PM in response to aimpromo

It's not at all uncommon for backups to be larger than the source volume.

Time Machine uses an incremental backup model based on snapshots - that is, the first backup is basically a snapshot of the source volume at the beginning of time, and for each increment it adds any changes.

This means that if your source disk contains 200GB of data on the first run, then you edit, say 100MB of documents before the next update, your backup will then contain 200.1GB.

Assuming you then edit another 500GB of data over the next day or so, your Time Machine backup is now 200.6GB

You might then delete 10GB of data, leaving 190.6GB of data on your source drive. Your Time Machine backup is 200.6GB (since it still contains the backup of the data that was deleted.

Following this model you can see that the backup will increase over time, way beyond the source volume content.

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Answer 2

aimpromo Author

Level 1

9 points

Oct 31, 2016 1:10 PM in response to Camelot

Hi Camelot,

Thanks for getting back. I hoped to make it clear (perhaps I didn't) that these to instances are brand new first time backups. For instance, I just completely deleted my backup on Time Capsule. I then started a new backup. When that backup finished,I checked it immediately and it was 900GB. The drive that was being backed up was 500GB, and it only actually contained 350GB of data. The brand new backup was hugely bigger than the drive. I have been using macs for 25 years and Time Machine since it came out, so I get the concept of incremental backups. I am talking a backup that is 3 times as large as the source data (or so it is reporting) from day 1. I don't expect this is a simple thing, but I am hoping someone has found a solution as I have read of other such issues.

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Answer 3

Oct 31, 2016 6:58 PM in response to aimpromo

You mentioned all computers are running the same OS but not which one.

What OS are you running??

When TM backs up to a network drive it creates a sparsebundle of suitable size.. that does not mean the data contained within the sparsebundle is actually the same as the container.

I am wondering if this is caused by having backups of so many computers and the problem of free space. Some recent changes in Sierra to Time Machine might explain it.

If you check pondini there is a method to compress the sparsebundle .. if you are concerned that is what I would do.. otherwise TM will not grow the space until the half full sparsebundle is full so that will work fine.

Pondini article.

Q12 here http://pondini.org/TM/FAQ.html

A8 here. http://pondini.org/TM/A8.html

He has a lot of info about over large backups and the causes.. which are numerous.

eg D4.. just go through the lists.

It is old but nothing else comes close to the details he includes.

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Answer 4

aimpromo Author

Level 1

9 points

Oct 31, 2016 8:31 PM in response to LaPastenague

OS El Cap 10.11.6 on every mac (5). The sparsebundle sizes are close enough to the amount of space occupied on each of the drives so is quite acceptable - ie less than 10 percent difference - on all but 2 computers. The sum of all the computers backing up still leaves about 1.5TB on the drive IF they backed up properly, but 2 drives are way over, claiming up 3 times as much space as is used on the drive. I actually formatted the Time Capsule drive tonight, and set each computer to do a new full backup, with the same result - 2 computers indicated that they were backing up 2-3 times more data than their drives contained. I removed all peripherals and external drives just in case.

I don't want to sound arrogant, but I could write most of the stuff in the Q12 link. I spent many of my last 25 mac years teaching basics and fundamentals. Partitioning the drives will "limit" a size, although you will just get a drive full message if you have 250 GB of data and limit a partition to 500, and then it wants to back up 900 because of some software glitch. Do you have an idea how to check individual file size allocations inside a sparsebundle. That migh help pinpoint way it is 3 times larger, or what type of file is the memory hog? The fact that it is only happening to 2 of 5 macs on the same OS, same net, and using the same backup is confusing me.

Just so you know, I really appreciate your input, and I am trying to get things figured out with your felp and on my own, not just waiting to be fed solutions, so Thanks!! I am sure the solution will come to light soon.

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Answer 5

Oct 31, 2016 8:52 PM in response to aimpromo

I think you might have missed the part about compressing the sparsebundle.

Do you have an idea how to check individual file size allocations inside a sparsebundle.

No.. the way TM works makes it exceedingly difficult to get that info. Files are broken up into bands..

But I think you should try and compact it. (I used the wrong word .. Compress.. it should be compact it). That will remove all free space inside the sparsebundle so you can see that it truly represents everything inside it.. If it still exceeds the size of the actual backup disk then I would be checking for some of the other things Pondini mentions..

Things do go wrong.. and it is exceedingly difficult because TM is a typical apple application with as little user understanding of what is going on as is possible. Do you for instance have a cache on those drives.. or virtual disk for parallel etc.. they can misrepresent their size.

Sparse bundles, however, have that "bands" folder in the sample above. All the directories, etc., plus the data, is spread over the "band" files inside it. Only the new or changed band files are considered as changed, so they're the only ones that get backed-up. On a large disk image, that can save lots of time and backup space.
The downside is, when things are deleted, the disk image doesn't shrink automatically. The vacated space is re-used for new data, then the disk image will grow again. There is a UNIX command to "compact" a sparse bundle, that will recover most of the empty space. That's the first thing Time Machine does when it's out of room. You can do it yourself if necessary; see the pink box in Time Machine FAQ #12 for instructions.

In Terminal, the prompt looks like this:
<ComputerName>:~ <user name>$

At the prompt, copy or type:
hdiutil compact
followed by a space:

Let me also suggest Time Machine has become rather fussy lately. I use Carbon Copy Cloner now as alternative.. it is going to work more reliably because it doesn't attempt the same level of archiving of old files.

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Answer 6

Oct 31, 2016 9:47 PM in response to LaPastenague

tmutils command does not have a total backup size that I can see..

https://developer.apple.com/legacy/library/documentation/Darwin/Reference/ManPag es/man8/tmutil.8.html

hdiutil I am not sure.

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Answer 7

Oct 31, 2016 10:49 PM in response to LaPastenague

Wish apple would give us a bit more edit time.

Checking through the info here. You would need to spend a bit of time to understand what it all means.. but it could be helpful in comparing backups.

hdiutil imageinfo /Volumes/Data/proimac.sparsebundle

Backing Store Information:

URL: file:///Volumes/Data/proimac.sparsebundle/

Name: proimac.sparsebundle

Class Name: CBundleBackingStore

Class Name: CSparseBundleDiskImage

Checksum Type: none

Size Information:

Total Bytes: 2998445457408

Compressed Ratio: 1

Sector Count: 5856338784

Total Non-Empty Bytes: 2998445457408

Compressed Bytes: 2998445457408

Total Empty Bytes: 0

Format: UDSB

Format Description: sparse

Checksum Value:

Properties:

Encrypted: false

Kernel Compatible: false

Checksummed: false

Software License Agreement: false

Partitioned: false

Compressed: no

Segments:

0: /Volumes/Data/proimac.sparsebundle

partitions:

partition-scheme: GUID

block-size: 512

partitions:

0:

partition-name: Protective Master Boot Record

partition-start: 0

partition-synthesized: true

partition-length: 1

partition-hint: MBR

1:

partition-name: GPT Header

partition-start: 1

partition-synthesized: true

partition-length: 1

partition-hint: Primary GPT Header

2:

partition-name: GPT Partition Data

partition-start: 2

partition-synthesized: true

partition-length: 32

partition-hint: Primary GPT Table

3:

partition-name:

partition-start: 34

partition-synthesized: true

partition-length: 6

partition-hint: Apple_Free

4:

partition-UUID: 9948A5AB-6DAE-4572-9E80-27618A067F67

partition-name: EFI System Partition

partition-hint-UUID: C12A7328-F81F-11D2-BA4B-00A0C93EC93B

partition-start: 40

partition-number: 1

partition-length: 409600

partition-hint: C12A7328-F81F-11D2-BA4B-00A0C93EC93B

partition-filesystems:

FAT32: EFI

5:

partition-UUID: 88EEB115-5419-44BB-B6F4-FFD47278794E

partition-name: disk image

partition-hint-UUID: 48465300-0000-11AA-AA11-00306543ECAC

partition-start: 409640

partition-number: 2

partition-length: 5855666960

partition-hint: Apple_HFSX

partition-filesystems:

HFSX:

6:

partition-name:

partition-start: 5856076600

partition-synthesized: true

partition-length: 262151

partition-hint: Apple_Free

7:

partition-name: GPT Partition Data

partition-start: 5856338751

partition-synthesized: true

partition-length: 32

partition-hint: Backup GPT Table

8:

partition-name: GPT Header

partition-start: 5856338783

partition-synthesized: true

partition-length: 1

partition-hint: Backup GPT Header

burnable: false

Resize limits (per hdiutil resize -limits):

min cur max

160299024 5855666960 68719476736

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Answer 8

aimpromo Author

Level 1

9 points

Nov 2, 2016 8:22 AM in response to LaPastenague

For lack of time at this moment, I took the advice of the last line of your post. I agree that Time Machine has become a bit fussy lately. It may come back to the ease of it's early days, but I have also gone back to Carbon Cloner and it is working perfectly and all is the correct size. Thanks for all your help. I will copy all this info for later reference, especially the sparsebundle compression option. I still have the huge sparsebundle, so it is worth a try.

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