The 2TB limit in Master Boot Record (MBR)


May 9, 2009
I keep seeing that there is a 2TB limit in the MBR, but I still don't fully understand what this means.

I'm wondering if it's just that a single drive can't be more than 2TB, or is it (essentially) that the OS cannot address over 2TB total?

I'm not looking for a technical explanation per say about it, but more how it actually effects trying to use a lot of HDs in windows OSs

Basically say I'm using windows 7 64bit, and I have a 1.5TB HD with it installed on it, can I not plug in a external drive that is 1TB and access all the files normally?

Now I've heard you can use other things other than the MBR to avoid the limit, I didn't do anything special when I installed this windows 7 64bit RC, so I assume its just using MBR, unless by default it uses something else.

Basically I'm wondering if this issue will effect me when trying to have windows 7 64bit be able to see more than 2TB of hard disks (spread over multiple physical disks, internal and external.)


Jun 1, 2009
It means you can not have a partition of over 2TiB with MBR or you'll run into troubles.
So if you just use a single 2TB drive by itself and make on big partition on it you can still safely use MBR. But say if you bunched up 4x1TB into RAID5, you get 3TB of usable space and if you want to make one partition out of it then you'll have to use GPT to overcome the 2TiB limitation of MBR.

The keyword of this limitation here as highlighted is "partition".
To be more specific, it means you can't have a BOOT partition more than 2TB. It's perfectly OK to create a 10TB RAID volume have one huge partition full of data, as long as you don't have to boot from it.

Windows has no problems accessing huge disks. For example individual files in NTFS can be up to 16 EXABytes in size, and the disk itself can be THAT size times the cluster size. That's enough to keep anyone happy for a few decades at least...

The boot partition limitation is in the BIOS protocols that are used to get the operating system loaded into memory. There are newer protocols designed to overcome that limitation (Google "GIUD partition table"), but they're not in common use yet.