29

GPT (GUID Partition Table) partitioning has some benefits over MBR (Master Boot Record), including Support for:

  1. More partitions (128)
  2. Drives larger than 2 TB

But are there any other benefits like less likelihood of corruption? (The two HD failures I've had were corrupt MBRs). Or are you just playing wack-a-mole where the GPT then gets corrupt in the same way?

Improve this question
1
  • 2
    Why is the corruption happening in the first place? Is it just that other sectors can get corrupt without being detected? – pjc50 Aug 17 '16 at 11:10
36

According to Wikipedia, there is redundancy in the GPT scheme. The GPT table is written at the beginning of the disk, as well as at the end of the disk (see image). In addition each GPT table has a CRC32 checksum.

enter image description here

The redundancy is not available in the MBR scheme (which only occupied the first 512 bytes of a disk). The extra redundancy would allow for more resilience against corruption. The CRC32 checksum allows the system to detect which of the two tables is the correct one to be used to repair the other.

Improve this answer
16
  • 1
    I wonder why they didn't go with three ... – Mawg says reinstate Monica Aug 17 '16 at 7:51
  • 5
    @Mawg Well, where would they put the third copy? Beginning of disk and end of disk are obvious places that don't mess with anything and are unlikely to be corrupted at the same time, but you can't just put a bunch of data in the middle of the disk. – Luaan Aug 17 '16 at 8:03
  • 1
    @Mawg: wel, putting the third copy in the middle of disk sectors will enforce you to have a partition split there. In this case you won't be able to move or shrink partitions cross that line (I mean LBA sector:). So that's impractical. And if you put 3rd one near 1st or 2nd one, then likeness of corrupting all the copies stays almost the same, IMHO. – saulius2 Aug 17 '16 at 8:46
  • 9
    @Mawg Remember that each copy has a CRC checksum, so that should tell you which of the two copies is corrupted on its own... – MathematicalOrchid Aug 17 '16 at 9:06
  • 2
    @Mawg you're looking for a solution for a hypothetical problem. If the two GPT tables don't match and if their CRC32 checkums are both OK, then you have indeed the problem you're describing. This would realistically only happen because of a serious bug in the operating system. Taking into account the disadvantages and problems with a third GPT copy (I think you might underestimate how complex partitioning can get in server environments), as well as a regression in functionality, I can well imagine that the designers opted for the non-nuclear-protection option :) – mtak Aug 18 '16 at 7:31

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.