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Can a >2.2 TB internal bootable hard drive be used in an iMac?

princealfie

princealfie

macrumors 68030
Original poster
Mar 7, 2006
2,517
1
Salt Lake City UT
I just installed a 4 TB hard drive into my 2006 iMac but I can't seem to figure out how to make it identify all 4 TB. It only does the 2.2 TB partition since it is MBR instead of GUID (UEFI) for the bootable drive. Any ideas what to do with all that extra space on my drive?
 
Startup from your Mac OS X reinstallation disc, go to the Utilities menu, select Disk Utility, click on your drive, go the partition tab, change the volume scheme to 1 (or as many as you want), click options, change it to GUID, click apply. Note: This will erase all data on the hard drive.
 
Thanks so basically will it allow me to use Windows 7 only and erase the Mac OS X portion or do I have to install Mac OS X along with Windows?
 
You shouldn't use a disk larger then 2.2TB with Windows using BIOS hardware. And on Apple hardware, it is effectively BIOS hardware as a result of the EFI CSM (Compatiblity Support Module) which Apple provides for supporting Windows.

BIOS booting Windows requires the boot disk use MBR partitioning scheme.

MBR has, in effect, a 2TB limit for the disk.

There are some attempts to get around this through partitioning, but none of the partition tools I've used on Mac OS or Linux will let you do this. They refuse to partition such disks using MBR scheme. Instead, you have to hand code your own partition scheme.

The way around this is UEFI booting Windows, instead of relying on the CSM. There are other threads discussing how to do this, with varying degrees of success. UEFI booting Windows requires the boot disk use GPT partitioning scheme.
 
The 2.2TB is a limit of the MBR partition scheme. It exists for all Macs running Boot Camp.
 
princealfie said:
Didn't work so ended up just setting my iMac to Mac OS X strictly. Kind of disappointing but maybe the newer iMacs can support it?
Click to expand...

If you partition the drive manually before installing both OS's to put the windows partition within the first 2TB, and the OS X one after it, it should work. Though, it might need hacking to get the MBR right as disk utility will probably not create a hybrid mbr for the drive.
 
iMacDragon said:
If you partition the drive manually before installing both OS's to put the windows partition within the first 2TB, and the OS X one after it, it should work. Though, it might need hacking to get the MBR right as disk utility will probably not create a hybrid mbr for the drive.
Click to expand...

Disk Utility definitely will not let you use MBR, nor create a hybrid MBR for a GPT disk, if the disk is larger than 2.2TB. And the command line utility fdisk for creating/editing MBRs will not work either. Nor will the Linux fdisk command.

It simply isn't recommended.

gdisk will create a hybrid MBR on a > 2.2TB disk that could work in certain circumstances, i.e. the starting sector LBA cannot be beyond the 2.2 TB limit, and the partition size for any partition cannot be bigger than the 2.2 TB limit. If Windows is to be in the last MBR partition entry (#4) then it would have to be 2.2TB in size, or waste the remaining disk space. If Windows were in the 2nd or 3rd position it could be a smaller size, but then it gets trickier how to protect and/or share the Mac OS partitions.

In any case it is so fragile and non-standard that you couldn't reliably allow anything to ever make disk partition modifications, or even understand the resulting partitions.
 
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