GPT vs. MBR: How the humble drive partition led to the larger hard drives we all love

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While installing Windows 8, Ragav RG converted his hard drive to the new GPT partitioning format. He asked about its advantages.

Before it can load an operating system, your PC needs a way of know where all of the partitions are located. Traditionally, it got that information from the drive’s Master Boot Record (MBR). But new computers are eschewing MBR for a newer and more versatile technology: GPT.

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And it’s about time. MBR dates back to 1983, when DOS-based PCs first used internal hard drives. MBR cannot easily manage drives larger than 4TB or with more than four partitions (there are workarounds, of course). GPT, on the other hand, has limits well beyond anything you’re likely to encounter over the next few decades.

GPT stands for GUID Partition Table—one of those annoying acronyms containing another acronym. GUID stands for  globally unique identifiers. Translation: Every partition has a randomly generated, 36-character Unicode name. It’s extremely unlikely that any two partitions in the world would have the same identifier.

Want to find out if your drive is using GPT? In the Start menu’s Search field or the Windows 8 Search charm, type partitions (you’ll need to type that s) and selecting Create and format hard disk partitions. In the resulting Disk Management program, right-click the drive’s gray box on the left. If you see a “Convert to GPT Disk” option—which will probably be grayed out—you’ve got an MBR drive. And vice versa, of course.

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GPT can speed up boot time compared to MBR, but I wouldn’t make a big deal about that. It can only speed up the first few seconds of the boot. And depending on your hardware, it may not speed it up enough to be noticed.

And what about Windows compatibility? Windows Vista, 7, and 8 can all read and write to GPT drives. But you can only boot from a GPT drive if you’re using a UEFI-based computer running a 64-bit version of Windows.

I wouldn’t bother reformatting a MBR drive to GPT. But it’s nice to know that your next PC will almost certainly use the new format.

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