I'm curious if others have noted anything similar to what I'm experiencing. If anyone has experienced it and discovered a fix, all the better! Time Machine has always been slow for me, but workable. I ran it on a 7200 RPM 500 GB hard drive inside of a USB 2.0 enclosure for a few years and even though a backup of less than 100 MB could take close to an hour with OS X 10.7 and 10.8, it always went through and I could recover data or my entire system from it if need be. A few months ago I came across a good deal on a 2 TB Western Digital Elements USB 2.0 drive. I reformatted it to remove in WD cruft and added it to my Time Machine preferences as a second drive. At this point I began to have issues, as I found that Time Machine was only backing up once every 3-5 hours instead of hourly. The problem was that backing up to the Elements - everything from copying the data to Time Machine "cleaning up" - took that long. My original drive would perform its backup in turn taking its usual 20-40 minutes, but then there would be another 3-5 hour gap. Disabling encryption on both drives didn't affect the speed. Swapping which USB ports they were plugged into didn't make a difference. Running the original drive alone caused Time Machine to go back to its usual slow yet reliable performance. Running the Elements alone still seemed to cause backups that took multiple hours even if they were under 100 MB in size. All of this would seem to imply that there was a hardware problem with the Elements, but disk benchmark testing indicated that the Elements performed slightly better than my original drive in read/write performance, including random reads and writes. While it seems incredibly unlikely and makes no sense to me, the conclusion that I'm coming to is that Time Machine has some sort of poor compatibility with this drive. Has anyone experienced anything similar?