Hi, I have a MacPro with 8TB of internal storage and roughly 3TB of data. I have been using a 4TB WD My Book Studio Edition II for Time Machine backup. A while ago, this WD external drive showed problems when it was stressed by an intense flow of backup data from Time Machine. TM failed to backup from time to time, and the disk became very hard to unmount (so even the verify and repair functions in disk utility cannot work well, since they require unmounting the disk). I returned the disk to WD and they gave me a working one. I don't know if it's new or repaired. Now, the same problem happened again. I start to wonder maybe this WD disk is not good for TM. Has anyone suffered from the same problem? This WD disk consists of two "green" WD 2TB disks (in RAID0, I believe). I heard that WD green disks are not good for RAID. Can this be the reason? The disks are user replaceable. Do you think I can just swap the two green drive with other ones and the problem will go away? If this can solve the problem, then I don't minding buying two other 2TB or even 3TB drives and use the two green WD 2TB in other places. On the other hand, if you think changing the disks will not solve the problem, could you recommend an external drive that's good for TM and can handle occasional very intense data flow from TM? I don't want to try WD again. I am thinking about the 6TB model from G-Technology. Any other suggestions? I know there are external disk arrays, but I prefer not to go through the trouble of setting up and maintaining them. A simple external disk that can just plug and go is better. Thank you for any suggestion on the WD drive and any other possible choices.