Lloyd Chambers, blogger and professional photographer, last week reported a serious bug with Time Machine on Lion and Mountain Lion OSes on his Mac Performance Guide site. The bug changes willy-nilly the Exclude these items... list, including the Boot and Master volumes, Chambers reports.
Excluded this way (silently and without warning), the hapless user (me) thinks that a regular hourly backup is happening when in fact it is not, the danger being that this could go on for days or weeks or months.
Most recently, Time Machine auto-excluded these critical volumes and then posted a dialog saying there was nothing to backup — this time I was lucky. Usually, Boot remains (so no such warning is issued), but Master alone is excluded — my most critical files left unprotected (in the short term, I do make clone backups regularly).
Even nastier, when I open the Time Machine preferences and un-exclude Master (after TM excluded it on its whim), it pops right back into the excluded list a short while later.
This is a very serious situation. Chambers noted the issue with Mac OS X Lion in the summer and now reports that it continues with Mountain Lion. He said he had reported the bug to Apple.
Chambers suggests in another post that relying soley on Time Machine for backup is a concern. I agree completely. For example, I use a high-speed external array for primary clones and backups as well as a cloud backup solution.
He points the finger at Apple's lack of focus on professional users.
Why do bugs like this happen? Perhaps because Apple increasingly thinks Macs are entertainment accessories with one drive (only), rather than a tool for getting work done (as prima facie evidence, Apple doesn’t even use the proper drive/disk versus volume terminology).
The wise course for backup is never assume and redundancy is mandatory.
Chambers also offers digilloyd Tools, a set of interesting utlities to test the performance and backup integrity. One of the tools is IntegrityChecker, which provides validation of data, including your originals and backups.
Validate the integrity of your files at any time, even backups on CDs or DVDs.
See which files have changed by date or size or contents.
Detect file corruption and/or inability to read files (e.g., on DVD or CD).
Have confidence your files are intact.
The other tools are Disk Tester, a performance tester and MemoryTester (you get the idea). The cost of all three is $39.99. Check them out, I will be.