Confused about Time Machine on 10.8

The screenshots and log excerpt are very helpful. The obvious problem is that Time Machine is reporting a nonsense value for the number of bytes to copy estimate, but the reason for this is a mystery.

Please confirm that you are using Snow Leopard. Your profile indicates

iMac (21.5-inch, Late 2012), OS X Mountain Lion (10.8.2)

... this is the Mountain Lion support area, your topic mentioned 10.8, and you said you purchased a "new iMac" which would certainly not be running Snow Leopard. Diagnosing what's wrong requires clarification.

Thanks for confirming that you're running Mountain Lion, that will help.

1. Did you install any Western Digital software that may have been included with the MyBook?
2. How did you initially erase the MyBook - did you use Disk Utility or something else?
3. Are you using any virtualization software e.g. Parallels, VMWare...?
4. Are you using any non-Apple "Anti-Virus" utilities - anything at all?

You did excellent groundwork on the problem.

Open the Time Machine pane in System Preferences. Click the padlock icon in the lower left corner, if necessary, to unlock it. Scroll to the bottom of the list of backup drives and click Add or Remove Backup Disk. Remove the problem disk, then add it back. Quit System Preferences. Test.

I restarted it in "safe mode."

Did you try to back up while in safe mode?

I know you verified your external drive with Disk Utility, but did you do the same for your internal boot drive? Try doing this to see if the source file system is intact or needs repair. It's possible a fault in this drive's formatting could be the reason for improper file size and file counts being read by the backup process.

The screenshots are very helpful.

Apple states that formatting the drive with Disk Utility is a requirement for Time Machine. I recommend you do not use Western Digital SmartWare regardless of prior experience with it.

The 131.8 GB of so-called "Additional Files" is clearly data put there by TM.

I agree but that is not likely to matter.

I suggest you do the following:

• Turn off Time Machine for now.
• Boot your Mac using OS X Recovery. At the OS X Utilities screen, select Disk Utility. At the Disk Utility screen, select your source volume ("Big Sister") and click Repair. Let it repair the volume.
• Still using Disk Utility, erase the backup volume. Select your backup volume ("MyBook" - be sure it is not your source volume), select the Erase tab, and next to Format select Mac OS Extended (Journaled).
• When it is finished quit Disk Utility, quit OS X Recovery, and restart your Mac.
• After it restarts, force Spotlight to erase and re-index your source. There is an Apple KB article that explains the procedure but it does not specifically indicate its applicability to Mountain Lion, so to be certain the Spotlight index is correctly erased and rebuilt, do the following instead:

You must first be logged in as an Administrator.

In Terminal, type the following:

sudo mdutil -E /

and press Return. At the Password: prompt, type your Administrator password followed by the Return key. The password characters will not be echoed, not even with ••• characters.

This will erase and rebuild the Spotlight index, which may take several hours.

You will know it has finished when clicking the Spotlight menu icon no longer shows a progress bar. When it does, re-enable Time Machine and select the backup volume.

I believe the cause of this problem is a corrupt Spotlight index, which may have been the result of using WD SmartWare, Onyx, or other unknown. Reformatting your backup volume and repairing your source volume are simply additional steps to ensure there is no obvious file system corruption that may have contributed to this.

Do not use Onyx to do anything. It may be harmless, but it cannot possibly help with anything.

Also, be sure to address questions 3 and 4 above. Anti-virus junk can interfere with Time Machine, and virtualization software can cause very slow backups.

In addition to removing the spotlight index on the boot drive, yoiu can also try doing so for your Time Machine drive. While you can do this using the command John Galt mentioned, you can also do it by dragging both of your drives to the Time Machine "Privacy" list (in the Time Machine system preferences) and then remove them from this list.

Splendid. Thanks for the follow up. This could have been vexing to resolve if you had not described your observations in such detail.

Preferences files are generally very small, inert, and can be ignored. There are exceptions, most of which are Microsoft-related. Others may be created by clever third party hacks that destablize your Mac and interfere with its file system, which is the reason for asking about AV software. I have not used any since Macs needed floppy disks, and even then there was only one that was useful.

I would avoid using any clever utility to identify and erase old Preferences files, or anything else for that matter. Use the Finder and sort Preferences files by Date Modified. If they have not been modified in years, then they are candidates for removal. If you are overly concerned they might be necessary, then drag them to a temporary folder and leave them there until you are satisfied they are no longer required. If you guessed incorrectly and a previously functioning program is demanding registration information (for example), just drag the Preferences file back to its original location.

Virtualization software includes various means of running Windows on a Mac. This results in thousands of small items and memory swap files that constantly change, causing Time Machine to run slowly. X11 is not that.

Thanks for the kind words. A few post-mortem comments:

• You can't erase an active Time Machine backup volume.
• Once you've erased it, there's no reason to rebuild the Spotlight index.
• It's not clear whether you tried to back up in safe mode.
• The WD software probably caused the problem, and may cause it again.