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Everything You Need to Know About 3TB Hard Drives

07.07.2011
We expect hard-drive capacity to grow over time. Now that hard drives have jumped from 2TB to 3TB, however, upgraders face some challenges: These new hard drives may have issues in some drive enclosures and in older PCs, which aren't prepared to address the entire capacity of a 3TB model. Even if you can work such storage into your system, it may not be in a single 3TB volume, but in a 2.2TB volume and a 800GB volume instead.

The problem with deploying 3TB drives relates to older PCs (those more than a few months old, in most cases), and stems from the formula 2^32*512=2,199,023,255,552, or 2.2TB--a hard-drive addressing scheme found in legacy BIOSs and operating systems. In that formula, 2 indicates binary, 32 is the number of bits allowed in a legacy disk address, and 512 is the number of bytes in a legacy hard-drive data block. If the BIOS, drivers, I/O card, or operating system in your PC still plays by rules that involve this formula, you'll have issues installing and using a 3TB drive.

This situation could have been avoided if the entire computer industry had future-proofed after enduring the that cropped up around the turn of the millennium. In truth, most vendors did--with the notable exception of Microsoft. The company chose not to implement support for anything larger than 2.2TB drives in any of its 32-bit consumer operating systems--including Windows 7. Microsoft even omitted support from 64-bit XP. If you were looking for a reason to move to , here it is--courtesy of a not so subtle (or particularly gracious) invitation from the industry giant.

Fortunately, you can find drivers and utilities that allow you to use a 3TB drive as auxiliary storage with any flavor of Windows, XP or later. I say "auxiliary" because you can boot Windows from a 3TB drive only if it's 64-bit Vista or 64-bit Windows 7--and then, only if you have a PC with an EFI/UEFI BIOS. EFI is Intel's Extensible Firmware Interface, and UEFI (United EFI) is the nonproprietary version based on the 1.10 EFI spec. EFI assumes the hardware and operating system interfacing chores from the BIOS after startup. The technology has been around since--you guessed it--the turn of the millennium, when the 137GB problems surfaced. Unfortunately, with no mainstream OS support from Microsoft (which is actually on the UEFI board of directors), most motherboard vendors saw no reason to implement UEFI before now.

The EFI technology component that allows the full utilization of drives greater than 2.2TB is called the GPT, or the GUID (Globally Unique IDentifier) Partition Table. GPT replaces the older MBR (Master Boot Record) scheme (which is subject to the 2.2TB limit) and allows partitions of up to 9.2 zettabytes (2^70)--a large, barely comprehensible number. Windows XP and later versions of the OS support GPT, but, again, only 64-bit Vista and 7 support it during the boot process.