MBR和GPT(分区)

MBR:Master Boot Record

GPT：Guid Partition Table (全局唯一标识符分区表)

GPT is the new standard and is gradually replacing MBR

MBR

The MBR resides at the very beginning of the hard disk and it holds the information on how the logical partitions are organized in the storage device

In addition, the MBR also contains executable code that can scan the partitions for the active OS and load up the boot up code/procedure for the OS.

For a MBR disk, you can only have four primary partitions. To create more partitions, you can set the fourth partition as the extended partition and you will be able to create more sub-partitions (or logical drives) within it。

As MBR uses 32-bit to record the partition, each partition can only go up to a maximum of 2TB in size。

typical MBR disk layout

缺点:

There are several pitfalls with MBR. First of all, you can only have 4 partitions in the hard disk and each partition is limited to only 2TB in size. This is not going to work well with hard disk of big storage space, say 100TB. Secondly, the MBR is the only place that holds the partition information. If it ever get corrupted (and yes, it can get corrupted very easily), the entire hard disk is unreadable.

GUID Partition Table (GPT)

It’s a new standard that’s gradually replacing MBR.With GPT, you can create theoretically unlimited partitions on the hard disk, even though it is generally restricted to 128 partitions by most OSes.

Unlike MBR that limits each partition to only 2TB in size, each partition in GPT can hold up to 2^64 blocks in length (as it is using 64-bit), which is equivalent to 9.44ZB for a 512-byte block (1 ZB is 1 billion terabytes).In Microsoft Windows, that size is limited to 256TB.

there is a primary GPT at the beginning of the hard disk and a secondary GPT at the end. This is what makes GPT more useful than MBR. GPT stores a backup header and partition table at the end of the disk so it can be recovered if the primary tables are corrupted. It also carry out CRC32 checksums to detect errors and corruption of the header and partition table.

优点:

This system doesn’t have MBR’s limits. Drives can be much, much larger and size limits will depend on the operating system and its file systems. GPT allows for a nearly unlimited amount of partitions, and the limit here will be your operating system — Windows allows up to 128 partitions on a GPT drive, and you don’t have to create an extended partition.

On an MBR disk, the partitioning and boot data is stored in one place. If this data is overwritten or corrupted, you’re in trouble. In contrast, GPT stores multiple copies of this data across the disk, so it’s much more robust and can recover if the data is correupted. GPT also stores cyclic redundancy check (CRC) values to check that its data is intact — if the data is corrupted, GPT can notice the problem and attempt to recover the damaged data from another location on the disk. MBR had no way of knowing if its data was corrupted — you’d only see there was a problem when the boot process failed or your drive’s partitions vanished.the protective MBR protects the GPT data from being overwritten.