Re: Dual Boot / Alternate Boot Questions

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David wrote:
Note: there are four primary partitions allowed. The extended
partition is a primary partition. The first logical drive in the
extended partition will be numbered 5.

Timothy Daniels wrote:
The Extended Partition differs considerably from a Primary
partition, and the volume numbering you present (with a gap for
the Extended Partition itself and "5" signifying the 1st logical drive)
would only be true if:
1) The OS were Unix/Linux/Solaris/etc, AND
2) There were 3 primary partitions in addition
to the 1 Extended partition

BUT... we're talking about WinXP (and NT and 2K) here.
In those (and probably previous) Windows OSes, there is
no gap in numbering between the highest numbered Primary
partition and the first logical drive within an Extended
partition. Here is an example of volumes in their physical
order on a hard disk and the corresponding entry in the
boot.ini menu file:

Primary partition 1 <--partition(1)
Primary partition 2 <--partition(2)
Extended partition, 1st logical drive <--partition(4)
Primary partition 3 <--partition(3)

I have actually just tested this to confirm it. I put 4 clone
copies of my WinXP OS on a 2nd hard disk in my
desktop system in the physical order given above,
identified eash OS by putting a folder on the Desktop that
indicated the volume's identity, expanded each OS's
boot.ini file to include 4 optional "partition()" selections, set
the 2nd partition "active", disconnected the 1st hard drive,
and started booting. The OSes that booted are indicated
by the above table.

David wrote:
Read your description above and my description. They are both correct.
You are allowed to have up to four primary partitions which are
numbered 1 to 4. The Extended partition is one of those primary
partitions and it may be numbered from 1 to 4 depending on where its
record is in the partition table contained in the Master Boot Record.
(MBR) You could have primary partitions numbered 1 and 4 with no 2 or
3.

The first logical drive in an extended partition is always partition 5
whether there are one, two, three or four primary partitions.

I'm afraid that is incorrect, David. The primary partitions will receive numbers first and then the first logical drive inside the
extended partition will be given the next available number. If you have
one primary partition and one logical drive inside an extended partition
the logical drive will be partition 2. If you have three primary
partitions and one extended partition with logical drives the first
logical drive will be partition 4.


There is a limit on the number of logical drives available in an
extended partition but I'm not sure whether it is 16, 24 or 32. My
memory is failing due to underuse.

With DOS/W9x it's limited by the available letters, 26 letters, A&B reserved for floppy drives and C reserved for the active partition, that leaves 23 letters for logical drives. With Windows XP and the ability to mount drives to NTFS folders the number of logical drives is unlimited.

John
.

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