Sorry I have been out of the office for a couple weeks. Interesting thread. First off, Erasing a drive is a separate operation from Zeroing a drive. Even though in Disk Utility the end of a write zero operation is to ‘Erase’, which just means create a new partition map and directory.

I have never seen your Logical Group error. In the past, if you wanted to change the *type* of partition map you had to use the re-partition portion of DIsk Utility which would give you the option (under the ‘option’ button, of all places) to choose different types of format. If you choose 1 Partition it is just like erasing the drive itself and you get to select the partition type, which you cannot do in Erase.

Doesn’t sound like that would resolve the Logical Group bug, but it is something to look at when you are erasing drive. This was the way you could change a drive from the old days that had an Apple Partition Map to a GUID, for instance.

I can’t tell you how many 3 and 4TB drives we have tested installed in every MacPro model since the first one. So far I have not personally nor had a customer have an issue with formatting them.

Rick