I have a Mac that I duel boot with MacOSX and Linux. My partitions are 1: EFI 209.7 MB disk0s1 2: HFS+ (MacOSX) 89.1 GB disk0s2 3: Ext3 (Data) 880.7 GB disk0s3 4: Ext4 (Linux) 28.0 GB disk0s4 5: Swap 2.0 GB disk0s5 I have downloaded and installed the Demo version of ExtFS. When I try to copy a file to my 880 GB Data partition, while booted in macOSX, it is extremely slow and uses 100% of my CPU. However, if I try to copy that same file to my Data partition, when booted into Linux, It is fast and uses very little CPU. At first, my Data partitions was Ext4, and had the same problem. I reformatted it to Ext3 to try to solve it. I don't have the same problem, when copying a file to my 28 GB linux partition.