3TB external + Mac os X = can't recon partition

Mac Os X doesn’t recognizes a 3TB partition on an external WD 3TB green drive that was used before as internal drive.

hdd: WD30 EZRX-00DC0B0 - SATA/64MC cache

os:  Mac Os X 10.8.?  (as internal) , Mac Os X 10.9.4 (as internal) , Mac Os X 10.6.8  (as external)  & Mac Os X 10.10  (as external) 

Hi,

I’m using a WD Green 3TB as backup disk in my computer as internal for more than on year. The drive was working fine by then with Mac Os X 10.8 & Mac Os X 10.9. 

I decided to work while traveling and put that hard drive in a external USB 3 enclosure to be able to use it while on my journey.

I’ve tested it on 2 laptops (with Os X 10.6 & Os X 10.10) and I always get the same result:

  • The physical drive of 3TB is detected (In disk utility I see as mention with it WDC WD30 EZRX-00DC0B0) but it’s partition shows as a grayed out (as unmounted) MS-DOS (FAT) partition named DISK2S1 of 3TB. I can’t mount the partition so can’t access my data. 
  • I could format the whole thing but this is not an option as critical work data is on it. 

Is it possible that I need a (e)SATA conection to be able so that the computer can recognize the partition?

At the moment I’m on a place where they have only older computers without SATA support.

Please help me as I’m getting a little desperate.

Thank you

I suspect that all may be well if you access your drive via SATA or eSATA. Some enclosures are configured with 4KB sectoring rather than 512B. This means that sector 0 will still be readable, but the boot sectors of each partition will be in the wrong place. Other enclosures are affected by a 32-bit LBA (2TiB) limitation.

fzabkar wrote:
I suspect that all may be well if you access your drive via SATA or eSATA. Some enclosures are configured with 4KB sectoring rather than 512B. This means that sector 0 will still be readable, but the boot sectors of each partition will be in the wrong place. Other enclosures are affected by a 32-bit LBA (2TiB) limitation.

Thank you for your answer fzabkar.

Do you know how I could fix this? Is there some tool I can use? Bare in mind I have no access to (e)SATA tech.

In my Disk Utility the “Verify Disk” is grayed out while it’s connected as an external drive.

I bough a new enclosure because my old had this 2TB limitation and I’m now stuck with this. (Here is the link to the product page, I’ve contacted the manufacturer with your answer).

The datasheet states that the enclosure supports 4TB HDDs and Windows XP 32-bit, but it is not clear whether both are supported in combination with each other. If this combination is supported, then this would imply that the drive would be partitioned in MBR mode, in which case the sector size would need to be 1024 bytes or greater. WD’s 3TB My Books, for example, use 4KB sectoring for compatibility with Windows XP.

BTW, I’m assuming that the internal drive was formatted with a Mac file system, not FAT.

I’m not a Mac user, so I don’t know which disc tools are available on that platform, but on a Windows box I would examine the file system with a disc editor such as DMDE. In particular I would look at sectors 0, 1, and 2. DMDE would also report the sector size, and it would help us to determine whether the enclosure was subject to a 32-bit LBA limitation.

fzabkar wrote:
The datasheet states that the enclosure supports 4TB HDDs and Windows XP 32-bit, but it is not clear whether both are supported in combination with each other. If this combination is supported, then this would imply that the drive would be partitioned in MBR mode, in which case the sector size would need to be 1024 bytes or greater. WD’s 3TB My Books, for example, use 4KB sectoring for compatibility with Windows XP.

BTW, I’m assuming that the internal drive was formatted with a Mac file system, not FAT.

I’m not a Mac user, so I don’t know which disc tools are available on that platform, but on a Windows box I would examine the file system with a disc editor such as DMDE. In particular I would look at sectors 0, 1, and 2. DMDE would also report the sector size, and it would help us to determine whether the enclosure was subject to a 32-bit LBA limitation.

Correct, the file system is Mac File System.

I couldn’t find software running on Mac os X that could do the trick but found Data Rescue that is detecting the partition unmounted and letting me recover it’s data on another disc. Maybe it can do more but when I saw it could recover those files with their folder hierarchy and original names I immediately started to recover the most crucial files.

At least I’m safe before trying to experiment with my disk.