Moving external USB disk to internal SATA on MacPro 3,1 system

A bit more to the story...

Before removing the 3TB disk from the USB external enclosure, the disk looks like this using "diskutil list" command:

MacPro:~ xxxx$ diskutil list

/dev/disk0

#: TYPE NAME SIZE IDENTIFIER

0: GUID_partition_scheme *960.2 GB disk0

1: EFI EFI 209.7 MB disk0s1

2: Apple_HFS SSD 959.3 GB disk0s2

3: Apple_Boot Recovery HD 650.0 MB disk0s3

/dev/disk1

#: TYPE NAME SIZE IDENTIFIER

0: GUID_partition_scheme *3.0 TB disk1

1: EFI EFI 314.6 MB disk1s1

2: Apple_HFS Seagate MacOSX 127.6 GB disk1s2

3: Apple_Boot Recovery HD 650.0 MB disk1s3

4: Apple_HFS Seagate MacBook_Backups 2.9 TB disk1s4

But when I removed the drive and put in slot 4 of MacPro 3,1 system I get this:

MacPro:~ xxxx$ diskutil list

/dev/disk0

#: TYPE NAME SIZE IDENTIFIER

0: GUID_partition_scheme *960.2 GB disk0

1: EFI EFI 209.7 MB disk0s1

2: Apple_HFS SSD 959.3 GB disk0s2

3: Apple_Boot Recovery HD 650.0 MB disk0s3

/dev/disk1

#: TYPE NAME SIZE IDENTIFIER

0: FDisk_partition_scheme *3.0 TB disk1

1: 0xEE 375.1 GB disk1s1

So the volume has changed from a GUID partition scheme to a FDISK partition scheme by just moving from external USB to internal SATA. How can that be? This info is part of the boot sector I thought? So by just moving the disk, how can this info change? Does the external USB enclosure do some sort of magic? Does it hide this info and tell OS X something different?

I tried something a bit different to get another clue - I put a WD disk from a WD external enclosure into the Seagate external enclosure and the disk also wants to be initialized. So it appears external disk enclosures do different things to different disks. Why is this? Seems like the enclosure should offer nothing more than an interface to the physical disk from the OS's point of view, but based on what I'm seeing right now, it's doing a bit of behind-the-scenes "magic" that changes when the physical interface to the disk changes (from external-USB to internal SATA or from one brand of external enclosure like Seagate to another brand of external enclosure like WD???

Anyone have any idea what is really going on and how to get this to work without physically having to back up the disk and then move and re-format and restore? This disk has almost 2 terabytes of stuff and that extra work will take a couple of days of copying files. Big disks are so nice except when problems like this crop up and cause long delays in trying to backup/reformat/restore for something as seemingly simple as moving a drive from an external to internal type of connector or from one external to another external.

Thanks....

This is definitely a normal spinning 3TB drive - no SSD involved at all. I have a 960GB SSD drive as the boot volume in one of the SATA slots (this is disk0), so it's not related to the 3TB drive at all.

So the only difference between the two different "diskutil list" commands is the first one is with the drive in the USB enclosure and the second is the same physical drive mounted in one of the internal SATA slots in the MacPro system.

So, the only thing that makes sense to me right now, is that the enclosure is monkeying around with the boot sector info on the fly, and somehow keeping that little bit of info to itself, rather than writing it out to the drive itself. Why in the world they would do this, or need to do this, puzzles me even more...

Perhaps they really don't want people moving these cheap external USB drives into internal desktop drives? The drive itself (for the Seagate external) was a Barracuda model ST3000DM001.

Thanks for the input.. will keep trying to figure out what's going on.

Didn't ever use any Seagate software - volumes were set up with Disk Utility originally and then used for the last year or two on a MacBook. Got a used MacPro a while back and have been wanting to do this since then.

That copy process will take more than 2 days of copying - assuming there are no errors. Big disks are such a pain sometimes...rrrrrrrrr...but a necessary evil I guess ;-)

Thanks for the input...

Just to clear up something about this issue that seems to have been brought up by a couple of comments:

The external drive works fine (after formatting) in the internal slot and gives the full 3TB of space (so far anyway).

The problem is that I really didn't want to have to copy the data to another drive while the original is in the external enclosure, then move it into a spare SATA slot, then reformat and then copy the original data back. This is a huge waste of time and unnecessary spinning of wheels getting nowhere as far as I'm concerned. But since after two days, nobody has had any way around this ugly effort.

Thanks for your input and will keep hoping someone can shed some light on what is really going on here.

Something weird is going on with the discussion website software - this reply from Grant Bennet-Alder does not appear in the replies but does appear in his activity. How strange...do replies just kind of partially disappear at times here?

Anyway, I agree, this does indeed make sense as to what's happening. Why in the world would disk drive manufacturers go to this trouble? They market their drives as being useable on both Windows and Mac systems. When I partition and format a disk I sure would think that the disk reflects my decision on how I want it to be configured not on the firmware doing magic in the enclosure and not really configuring the drive as how I wish to do it, but hey, that's my error it appears ;-)

Thanks for the insight...