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Why does my TM/TC back up so much?

576 Views 11 Replies Latest reply: Aug 3, 2012 9:46 AM by Pondini RSS
iBozz Level 1 Level 1 (90 points)
Currently Being Moderated
Jul 28, 2012 10:35 AM

Before I refer this to AppleCare, I wonder if anyone on this forum can help?


I am waiting for AppleCare to call me back on another matter, but my excellent Level 2 geek is on hoiday so it may be a while before he comes back to me.


The reasons I am dealing with AppleCare, in case they are relevent to this current problem, are:  replaced optical drive, replaced video card, replaced LCD - all at 30 months old and all in the past 6 weeks!  Also, duplicated iCal/Calendar events and non-sync'd events between my iPad and iMac (now resolved, a corrupt version of iTunes) and more latterly a suspected corrupt partition map on the iMac as I cannot create a new partition.


But, on the assumption that those do not affect my Time Machine to Time Capsule transfers, here is my current problem ...


I run a 27" i7 1TB iMac with 16GB of RAM under MacOSX.6.8 and I have recently acquired at 2TB Time Capsule, to which I backed up my 669.45GB full HD via Ethernet.  I am now backing up the iMac wirlessly.


I have a G4 Tower and a G4 eMac, both running under MacOSX.4.11, on my network and they appear on my iMac's Desktop as networked devices.  I have an Alias to my HP DeskJet 840C printer which is connected to the eMac by wire and I have Chicken of the VNC as an Alias so that I can lazily control the two G4s from the comfort of my lounge should the rare need arise!


I run Stanford University's Folding@Home v7.1.52 24/7 and that is the only User process which, to the best of my knowledge, runs when the iMac is unattended.


I back up a 64GB iPad [3] via iTunes to the iMac from time to time, but there shouldn't be massive changes in that.


So why are my backups seemingly so large?


So large, in fact, that several take over an hour so that the default hourly backups are "late" and the iMac seems to be backing uop non-stop!


I have, in an attempt to stop cache files, etc, excluded from backing up (in case they changed so often that they might account for the number of files allegedly copied, if not the size) the following ...





~/Library/Appliction Support/TechTool Protection


I have seen posts on this forum that advise excluding the Time Machine file and network disks from backing up, but when I go to TC Preferences, I cannot find them shown so I cannot exclude them.


Each back-up appears to be in two parts, as demonstrated by the following most recent log ...


Starting standard backup

Attempting to mount network destination using URL: afp://Roy@Sue.local/Data

Mounted network destination using URL: afp://Roy@Sue.local/Data


Disk image /Volumes/Data/Roy’s iMac.sparsebundle mounted at: /Volumes/Time Machine Backups

Backing up to: /Volumes/Time Machine Backups/Backups.backupdb

No pre-backup thinning needed: 12.91 GB requested (including padding), 738.07 GB available

Bulk setting Spotlight attributes failed.

Copied 44382 files (8.5 GB) from volume Grumpy.

No pre-backup thinning needed: 3.46 GB requested (including padding), 738.00 GB available

Copied 34176 files (613.5 MB) from volume Grumpy.

Starting post-backup thinning

Deleted backup /Volumes/Time Machine Backups/Backups.backupdb/Roy’s iMac/2012-07-27-162213: 737.39 GB now available

Post-back up thinning complete: 1 expired backups removed

Backup completed successfully.

Ejected Time Machine disk image.

Ejected Time Machine network volume.



... first it asked for 12.91GB and then 3.48GB - massively larger than i would expect for a machine left unattended all day.  It backed up less, but that's what it asked for.


And 44,382 and 34,176 files respectively?  Where on earth did they come from.  I'm aware, or think I am aware, that many seemingly single files are in fact a number os smaller files - but even so!


Recent sizes backed up, for which logs are still available, are (in GBs) ...


96.55 + 4.62

12.76 + 12.76

2.79 + 4.03

3.50 + 2.76

3.34 + 2.79

2.79 + 14.02

3.43 + 12.80

96.67 + 12.86

12.97 + 2.87

3.48 + 2.87

12.88 + 3.40

3.44 + 2.84

3.44 + 2.87

2.88 + 12.85

3.44 + 2.87

3.44 + 2.84


Note the two of them at over 90GB!  What on earth are those?


I'm pretty sure that TC is an incremental back-up so I would have expected much much smaller files!


Anyone help whilst my excellent AppleCare contact is away will be very much appreciated!




Message was edited by: iBozz to correct sloppy typos

27" quad-core i7 iMac, Mac OS X (10.6.8), 16GB RAM; G4 eMac & Tower; iPad 4G
  • Bob Timmons Level 9 Level 9 (75,445 points)
    Currently Being Moderated
    Jul 28, 2012 10:38 AM (in response to iBozz)

    It might help to find out exactly which files are being backed up on each pass.


    For that, a utility like BackupLoupe will provide some information. Cost is $4 or 5 as I recall.


    soma-zone: BackupLoupe

  • Pondini Level 8 Level 8 (38,710 points)
    Currently Being Moderated
    Jul 28, 2012 12:58 PM (in response to iBozz)

    iBozz wrote:

    . . .



    Those are excluded automatically.


    I have seen posts on this forum that advise excluding the Time Machine file and network disks from backing up, but when I go to TC Preferences, I cannot find them shown so I cannot exclude them.

    A directly-connected TM drive is excluded by default.

    Time Machine cannot back up any drive on a network, so no, you can't, and don't need to, exclude them.



    While you're waiting for BackupLoupe, you might want to check #D4 in Time Machine - Troubleshooting for some common culprits.

  • Pondini Level 8 Level 8 (38,710 points)
    Currently Being Moderated
    Jul 28, 2012 3:16 PM (in response to iBozz)

    iBozz wrote:

    . . .

    identified a Sparse Disk Image file of around 75GB as being the major component.

    A sparse disk image will be backed-up in full if there are any changes to it at all.


    A sparse bundle disk image, however, won't.  Sparse bundles are rather odd critters; they consist of 8 MB "band" files (thousands, in a large one); the contents of the disk image are spread across them. 


    When you make a change to a file there, only the changed bands are treated as changed and backed-up. 


    When you delete a file, the bands it vacates aren't deleted;  they'll be reused when new files are added, before adding new bands.  The downside is, if you delete a large file or folder, you don't get the space back.  But there is a way to "compact" them, via a Terminal command. 


    Time Machine stores backups made over a network in a sparse bundle, too.  The pink box in Time Machine - Frequently Asked Question #12 shows how to "compact" one.



    So, if those sparse disk images are a problem, you might want to use sparse bundles instead, if possible.

  • Pondini Level 8 Level 8 (38,710 points)
    Currently Being Moderated
    Aug 3, 2012 8:31 AM (in response to iBozz)

    iBozz wrote:

    . . .

    ~/Library/Application Support/SyncServices/Local

    That's part of iSync.   I don't use it (and it was discontinued effectrive with Lion)


    The other largish folder to backup every hour, even when the iMac is left unattended and thus doing nothing except Folding@Home and routine OS matters, with around 35MB is .Dropbox (not ~/DropBox).


    Why does this change and can I safely exclude it?

    That's got something to do with keeping track of the status of syncing files to their servers, and yes, you can safely exclude it (you have to select the Show invisible items box on the exclusion window).



    I know it is like asking "How long is a piece of string", but how long should I expect the hourly incremental; back-ups to take - roughly?  50 minutes out of every 60 minutes seems a shade too long to me.

    It does vary widely, depending on a number of things, most the size of the backups.  But as a very rough example, a recent wireless backup of about 180 MB took just under 5 minutes (that's actually a bit high).  Note that if expired backups are deleted, that will take some time, too.

  • Pondini Level 8 Level 8 (38,710 points)
    Currently Being Moderated
    Aug 3, 2012 9:46 AM (in response to iBozz)

    iBozz wrote:

    . . .

    A rough average back-up would, according to BackupLoupe, be around 80MB to 90MB - before the two changes which I have just mentioned take effect, yet appear to be taking somewhere around 45 or so minutes!

    That's awful. 



    Bulk setting Spotlight attributes failed.

    . . .

    Bulk setting Spotlight attributes failed.

    That's a problem with the index on your backups.  Looks like you get them on every backup.


    Copied 48532 files (73.4 MB) from volume Grumpy.

    . . .

    Copied 37164 files (53.1 MB) from volume Grumpy.

    Those seem like a problem we've seen on occasion with 10.6.8.  Huge file counts, but small sizes, and very slow backups.  The file counts are always high (apparently it counts every permission and extended attriibute separately), but not like that.


    I'd recommend starting with the green box in #D2 of Time Machine - Troubleshooting.  I suspect nothing there will help much, but it's worth a try.


    I suspect your problem is actually with 10.6.8.  If you get to #16 in the green box, what's worked for a few folks in this situation is to install a fresh copy of Snow Leopard, then install the 10.6.7 "combo," not the 10.6.8 version.


    The downside to that (besides all the hassle), is the bug in Snow Leopard that wasn't fixed until 10.6.8.  See the 3rd item in #D5 of the same link.


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