Page 1 of 1
Partitions in MBR
Posted: Thu Feb 13, 2014 9:03 am
by randoll
I am little bit confused why does MBR has this table marked as reserved.
Is it ever used by firmware like GPT in UEFI?
Or is it only used as standardized signal in between installers?
Re: Partitions in MBR
Posted: Thu Feb 13, 2014 9:22 am
by iansjack
Is it possible to explain what you are talking about? Which table?
Re: Partitions in MBR
Posted: Thu Feb 13, 2014 9:23 am
by Combuster
Since "this" could only possibly refer to partition tables... (And yes, I agree that the formulation is horrible)
The partition table in the MBR is not technically "reserved space". The MBR is simply the first sector of a storage medium. It can have a partition table but it's not mandatory. Look at floppies which rarely have a partition table, SD cards where there's practically always one filesystem and occasionally without the single-entry partition table, or even CDs which has an entire replacement system for partition tables (just like GPT is a replacement).
EFI only needs a GPT - located in the second sector. The parition table isn't necessary, but it might exist to have both EFI and legacy OSes on the same machine - or even to simply prevent legacy stuff from messing up the disk by making it look like everything is in use.
Re: Partitions in MBR
Posted: Thu Feb 13, 2014 11:07 am
by iansjack
I thought the reason for the partition table in an MBR was too obvious to need questioning. (How else is an operating system to know where to find the partitions on an MBR formatted disk?) Perhaps I am reading more into the question than is there.
Re: Partitions in MBR
Posted: Thu Feb 13, 2014 11:32 am
by randoll
Why is there partition tables in MBR mostly reffered as standard?
From what does it come from?
Re: Partitions in MBR
Posted: Thu Feb 13, 2014 11:47 am
by Combuster
Re: Partitions in MBR
Posted: Thu Feb 13, 2014 11:50 am
by Brendan
Hi,
randoll wrote:I am little bit confused why does MBR has this table marked as reserved.
Is it ever used by firmware like GPT in UEFI?
The MBR's partition table isn't normally used by firmware. If the firmware is UEFI it uses GPT, and if the firmware is BIOS it normally doesn't know or care about partitions.
randoll wrote:Why is there partition tables in MBR mostly reffered as standard?
Some standards are "de facto standards". The MBR partitioning scheme is what Microsoft invented for their OSs, and everyone else on 80x86 ended up either adopting it or tolerating it to avoid compatibility problems. For an example, BSD had its own scheme ("slices") before Microsoft decided to use the MBR partitioning; and to avoid compatibility problems BSD on 80x86 ended up having "partition of slices" instead of just "slices".
randoll wrote:From what does it come from?
The partition table itself comes from tools that create/manage partitions. This could be a stand-alone tool (e.g. "fdisk" utility) or an OS installer.
Cheers,
Brendan