(mbr)
One of the four partitions on the disk can be the Extended Partition. It can be subdivided into logical volumes.
in windows:
Each logical volume is assigned a disk letter and can be formatted with a separate file system. There is no limit on the number of logical volumes other than the fact that there are only 26 letters in the alphabet and A, B, and C have been taken
in Linux systems:
why you cannot creat over than 12 logical partition in Linux system(fdisk) ?

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What distribution/version are you running? That is correct the maximum number of partitions for a legacy MBR is 16 based upon the SCSI subsystem drivers. All drives no matter PATA, SATA, USB etc use the SCSI subsystem.

is this difference between mbr in windows and mbr in Linux?why you can create 22 logical partitions in windows but in Linux you can craet just 12 logical partitions in the same system?what is the max number of logical partitions in mbr ?

It is basically driver / software dependent and nothing to due with the physical hardware. With the old linux IDE driver the limit was 63 partitions.

Actually with a few tricks one create more then 15. The site is down at the moment and forgive me for posting a link from another forum but sekai has played a lot with partitioning drives.

http://forums.justlinux.com/maintena...-PATA-USB-disk

BTW the total including primary partitions is 16.

The limit is imposed by the scsi drivers (i.e., 'sd' drivers). The logical partitions are not a property of the mbr, in fact they were devised in order to overcome limitations of the mbr. So asking, "what is the max number of logical partitions in mbr?" is not a valid question, the answer is zero!

Using the IDE drivers (i.e., 'hd' drivers) there was a limit of 63 partitions, but with the sd drivers the limit is 15, 3 of which may be primary partitions, so the limit for logical partitions is 12.

You can in fact create more than 12 logical partitions under GNU/Linux, but many programs and utilities will become confused by them, so it is best to stay with 12 or fewer.

Actually, it is pretty easy to overcome this limitation: Just don't use MBR style partitioning, use GPT style partitioning. Any modern Windows (if you have an UEFI BIOS) or Linux (works with any BIOS) version should be able to handle that just fine*.

* Windows has some artificial limitations in GPT support that can be seen in the corresponding Wikipedia article: http://en.wikipedia.org/wiki/GUID_Pa...2-bit_versions

Actually one could make 52 disks in dos. When you ended with z you started with aa and so on.

You can really make hundreds of partitions. Many tools have been made over the years to fool the system. I have seen some tools that had made 100 OS's run on a mbr disk.

Answered before also. https://www.linuxquestions.org/quest...tition-754458/

sorry but I tested with ide driver and same result again.both scsi or ide driver in fdisk tools you cannot create over than 12 logical partitions.....

Well, you make a lot of assumptions with that!

As I said earlier, the limit with the older IDE hd drivers was 63 partitions - that is history.

And the scsi sd drivers now commonly in use impose a limit of 15 partitions, 3 of which may be primary, leaving a limit of 12 logical partitions - the current state of affairs.

But while the drivers impose the limit, they may not be the thing that enforces the limit - that may be done by various tools, including fdisk itself. So reverting to the older drivers may not be sufficient to completely revert to the old behavior and restore the 63 partition limit across the board.

As I said, although you can still create more than 12 logical partitions, many programs do not recognize them - it runs deeper than just the drivers at this point!

I really don't know how each tool, the BIOS, or even the kernel may decide how many logical partitions to allow, but I expect it goes deeper than simply loading a different driver.

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