Ext partition - why so ugly way to have more than 4

[suslik]

I wonder why did Microsoft/IBM introduce Extended partition in MBR to have more than only 4 partitions? I suppose this could be done more easy: 1) reduce code part: 382 bytes are enough and in this case we have 8 partitions descriptors! 2) extend partition table to the next sector: in this case we have 4+32=36 partitions! Yep, not infinite... but more than enough.

[Nable]

Almost no-one uses them (because there are better ways of dividing disk space) so why would anyone bother?
Btw, HDDs were ~10-100MiB when people started using MBR scheme, keep it in mind.

[iansjack]

If it ain't broke then don't fix it.

The current system works just fine. Changing it could break all sorts of things, so why bother?

[Brendan]

Hi,

If it ain't broke then don't fix it.

Problems with the MBR scheme include:

• A single sector controls everything, and if anything happens to that single sector (e.g. it becomes faulty) you're doomed (no redundancy).
• No sane/standard way to have more than one bootable partition
• Partition sizes are limited to 2**32 sectors (2 TiB for 512-byte sectors) and partition start is limited to 2**32 sectors, which limits the size of disks (including large RAID arrays) that can be supported to a max. of 2**33 sectors (4 TiB for 512-byte sectors)
• The 8-bit "partition type" field wasn't enough (some IDs are used by 2 or more different file systems)
• No way to give a partition a human readable name, resulting in file systems that include their own "label" and OSs that have to support a file system before they can get the partition's name. Also makes "spare" (deliberately unformatted) partitions unnameable.
• No way to give a partition a unique ID, so that if a partition is moved (e.g. hard disk replaced) an OS can't find it anymore

For these reasons, MBR partitions was replaced by GPT. Basically, it was broken and was fixed.


Cheers,

Brendan

[iansjack]

I have to disagree. The original MBR scheme is not broken - it works just fine on millions of computers. And it wasn't fixed, or replaced, an alternative was developed. Would you like to take a bet as to which is still the primary method of partitioning a hard disk in a PC?

I've no objection to improved versions being developed, but fixing implies changing the existing version. This would probably break millions of existing installations so is not a good idea.

For these reasons, MBR partitions was replaced by GPT.

Millions of PCs would take issue with that statement.