I changed my 4TB SATA HDD to a different 3.5 inch USB enclosure.
When plugging the new enclosure's USB cable into my Windows 7 x64 PC, in the Disk Management MMC, it asked to be initialized with MBR, and I consented. I now have two 1.8TB drives without data.
Is there a way to go back to a GPT partition table and recover the data that was originalky on the drive?
It's possible that the GPT backup data, and maybe even the primary GPT data, remain intact. If so, my GPT fdisk (gdisk) utility should be able to recover the original partitions. See the gdisk documentation's page on data recovery for some basic information and advice.
Two important caveats:
Note that partitions are just chunks of the disk, as defined in a partition table. Filesystems are more complex data structures that are typically stored within partitions. Although many tools manipulate both together, they're different data structures, and understanding this distinction can be critical for data recovery. In particular, gdisk is a partitioning tool that doesn't touch filesystem data, so gdisk may be able to help with the partitioning issue, but if there's filesystem damage gdisk can't help with that.
testdisk, a popular open-source tool to search for and salvage partition metadata, may be able to help you here. While other tools (such as Recuva or photorec, the latter being from the same company that makes testdisk) will search your partitions for traces/remnants of your files and attempt to rescue them, testdisk will search for lost/overwritten information about where your partitions were originally located and what their structure was like (filesystem, start sector, length, etc).
If you're lucky, testdisk might be able to simply virtually undo all changes you made by either rebuilding or recovering the GPT structure.
If you've written data to the disk (other than simply creating a new, incorrect MBR), your odds of recovering the data are considerably reduced.
Some files or file directories are likely to be lost, but you should be able to recover most of the file data this way:
If you have another machine with an OS that supports GPT, first install an unerase utility.
Then attach the drive, delete the MBR partitions so the drive is completely unallocated.
Then create the single GPT partition but opt for quick formatting.
This will create empty file tables, but not delete the file data.
Then run the unerase utility. This will find both valid files and old delete fragments. Hopefully there will be enough structure left to recover anything critical.
I just bought a new 2TB disk drive I plan to use as an external drive (connected via eSATA). When I started my computer it recognized the drive fine, but when I got into the Disk Management, a popup told me that I have to initialize that drive and I have to choose between MBR and GPT layout.
The drive will be primarily used on Windows 7 computers (both x86 and x64) as well as on a Windows Vista x64 computer (which is the one the message appeared on).
I do not plan to create multiple partitions on that drive as it is only supposed to be a data storage disk.
Which partition layout should I choose, MBR or GPT? The dialog itself recommends to use GPT on drives >= 2TB or on Itanium based computers, but I want to make sure that I will be able to access the drive later on my other computers.
GPT will not be usable by XP and earlier systems (I think), so avoid it if that is an issue. Not having seen an XP machine in 3 years it's not an issue for me so I use it in preference to MBR, but it makes little difference at this point in time. At some point, you will have to use GPT, until then, make a choice.
As of now, support for GPT among common systems is limited. Check out the list of supported OSes here: http://en.wikipedia.org/wiki/GUID_Partition_Table#OS_support_of_GPT