You may be aware that Lion introduced MTMFS, the Mobile Time Machine File System.
I've had a couple of instances now where MTMFS has been chewing up an entire core of my dual-core (mid 2009) MacBook Pro for hours on end with no evidence that it's actually doing anything constructive.
As a consequence, CPU temperature rises and the cooling fans run fast and noisy.
Restarting the machine quietened things down again, but I'm expecting it to start again.
Does anyone understand MTMFS well enough to suggest why it's keeping itself busy (or is it most likely, simply a bug), or if there's currently any solution? I fear I may have gone deaf or been scalded to death before Apple release an update…
Best Answer
I suffered this today when doing a find / -whatever -exec this-or-that {} \;
Suddenly mtmfs got 100% CPU. It turns out that mtmfs is a special filesystem mounted on /Volumes/MobileBackups. If you run something that will access files indiscrimately, such as a find (something many "cleaner" programs do) mtmfs will use a lot of CPU when its files are being accessed.
You have two options:
1) As suggested, disable local Time Machine backups (sudo tmutil disablelocal)
2) Make sure to exclude /Volumes/MobileBackups (or even /Volumes, as it can be a p.i.t.a. to run a find over network file systems) from the search command.
That should solve the issue.