MTMFS consuming an entire CPU core and fans running full bore with Lion 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...
To track down the issue you may have to dive into fs_usage or other tools that capture filesystem activity as it happens.

Normally, I have seen minor corruption issues on a filesystem (or bugs in the code - it's hard to tell / hard to reproduce this issue) as the cause of this. In practice I can't get it to fail again after cleaning the existing local backup.


sudo tmutil disablelocal
reboot the Mac in safe mode (which runs fsck and many other helpful and potentially irrelevant tests and checks for corruption)
reboot the mac normally
sudo tmutil enablelocal