▷ What is a gpt partition and what are its advantages

Many of us have formatted the hard drives of our team a huge number of times, either to renew our operating system, to solve errors or to create new partitions or install another system such as Linux. And it also happens that we have practically never paid attention to the style of partitions that our system uses, since in most cases we will simply use the default Windows or Linux wizard without paying attention to details.

Currently there are two types of partitioning styles, MBR and GPT, and both have the mission of preparing our hard drive to host, and boot our operating system. But it is much more than this, so today we are going to explain what the GPT partitioning style consists of.

What is a GPT partition

When we talk about a GPT partition, we are really talking about a GPT partition table or also called GUID partitions. The GPT style is nothing more than a partitioning standard for placing the partition table on a physical hard drive.

Our hard disk always contains a partition table that determines its structure of active, logical or extended partitions, as well as a startup code so that our operating system can be executed. We have always known this partition table as MBR or Master Boot Record and it has been in charge of performing the actions we have discussed.

Well, GPT is nothing more than a different style of partition table, which was implemented for modern EFI systems or Extensible Firmware Interface, which has replaced the old BIOS system of computers. So while BIOS uses MBR to manage hard drive and system boot, GPT is geared towards being the proprietary system for UEFI.

The name it receives from GUID or GPT comes from the fact that the system associates a unique global identifier to each partition (Global Unique Identifier). The GUID name extension is so long that we could name all the partitions in the world with a different unique identifier, so there are no limitations for this style of partition beyond those of the hard drive and system itself operational. For example, Windows has a limit of 128 primary GPT partitions.

Characteristics of GPT partitions and difference with MBR

Like an MBR partition, a hard drive with a GPT partition table begins the drive with an MBR entry for mere compatibility purposes with older PC BIOS systems. But it is really based on the capabilities of the EFI itself to carry out the management and startup processes of the disk content, remember that a UEFI creates its own boot menu if we tell it to do so. Instead, MBR implements an executable to identify the active partition and to start the boot process.

This means that GP T changes for example the addressing system of our hard drive. While the MBR uses the traditional CHS or Cylinder-Head-Sector system to send the data addresses to the device, GPT does it using LBA or logical block address to refer to the region where the data physically stored in our unit is located. of storage.

Another major difference between MBR and GPT is the limitation of partitions and their size: with MBR we can only create four primary partitions and not larger than 2 TB each. For example, on a 16 TB hard drive we would already have this limitation in both aspects. In GPT there is practically no type of limitation except for the operating system and the hard disk.

Structure of a GPT partition table

Now let's talk about the distribution of information that we could find in a GPT partition table. As we said, in the beginning there is a piece of MBR code to provide compatibility with older BIOS systems.

But this partitioning style also stores a backup copy of this complete partition table right at the end of the hard disk. This way we will have the same information both at the beginning and at the end of the disc. In the 64-bit Windows operating systems, which are the most used, for each of these tables a total of 32 sectors of the hard disk have been assigned, or what is the same, 16, 384 bytes of storage. Each of the LBA logical blocks is 512 bytes in size. Let's see what they contain:

LBA 0:

GPT maintains an MBR early in the structure to provide compatibility with older disk management tools. Specifically, this MBR specifies that the hard drive contains a single partition that spans the entire GPT drive. UEFI systems directly ignore this piece of code.

LBA 1:

Information about the disk blocks that users can use is stored inside the first block, in addition to the number and size of partitions that exist. In Windows we can create up to 128 partitions on a GPT hard drive, compared to only 4 in the MBR system.

This header is where the GUID of the disk is located, as well as its size and where the secondary partition table (the backup) is located. Finally it contains a CRC32 checksum for EFI to verify that everything is correct and proceed to boot.

LBA 2 to 33

The corresponding partition entries will be stored in the following logical blocks. The partition type (16 bytes), the unique GUID of the partition (16 bytes), and other information up to a total of 128 bytes are stored in each of these entries. This is why each logical block can store information from 4 partitions (128 × 4 = 512).

An identifier for a partition could be:

EBD0A0A2-B9E5-4433-87C0-68B6B72699C7

Specifically, this is the identifier of the Windows data partition, which curiously coincides with that of Linux.

Is it recommended to convert our hard drive to GPT?

Today we have to say that it is recommended to convert our hard drive to GPT, in fact, many new preformatted drives, especially laptops, already come with this style of partition implemented. So if we have an EFI version of BIOS, we do recommend using this style.

With GPT we will obtain greater security on our hard disk in terms of data loss, since we have a copy of the partition table itself replicated on our disk. This will be especially useful if we have hard drives larger than 2TB to remove the limitations of MBR partitions.

On the other hand, the installation of Windows on this type of hard drives is more complex, and it is necessary to do a trick than another, since we will have to have the UEFI type boot mode or inherited BIOS mode activated on our computer to be able to install The operating system. In other tutorials we will cover these topics in more detail on how to work with a GPT hard drive.

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