Macos – Mac’s hard drive is filling itself

This is a few years after the question was posted but it will help someone else. I saw the major part of this answer somewhere else and I'm not sure if the -c option was available in older ddrescue. -c changes the amount of sectors to copy at a time.

here goes:

ddrescue -d -r0 -e +0 -T 1s -n /dev/sdX recover.img recover.log -c 1 -O

replace X with the drive you are trying to recover. Data will be stored in a file called recover.img so you'll need enough space.

Use the 'watch' program in front of the above code to run the code automatically when it crashes due to 'too many bad areas' error.

From my experience, Yosemite is using a lot more RAM than 3GB if you run it natively (no emulation). I imagine in virtualised mode it would take even more. I have 16GB installed on my system and Yosemite is using about 4-5 GB without any application running. Once I open other applications and run one or two virtual machines the available RAM can go down almost to under 1GB.

Virtual machines use a lot of RAM in Yosemite for creating file caches. For example, if I run a Windows XP or Mountain Lion VM in VMWare on a base Yosemite system and allocate about 4GB of RAM, VMWare will use more than that for caching files.

This is done for speed purposes, so that if you close the VM and want to open it later, it will take much less time to resume the VM if there is a file cache in RAM, than if there isn't one. You can test this by running sudo purge in the Terminal after you close a virtual machine, then re-opening it. You will notice that resuming the machine is much slower than if you didn't purge the RAM of the file cache.

Also, VMWare seems to not work well/recognise graphic cards in virtualised OS X. For example, I created two virtual machines, one with Windows XP and one with Mountain Lion. The Windows VM can play the same game, altough it's laggy even with 8GB allocated RAM, whereas the OS X VM can't even open the game, the application crashes at start. Which means the virtualised OS X doesn't even recognise there is an emulated graphics card.