Order in Which MS-DOS and Windows Assign Drive Letters

[GWHSU]

Question about drive letter assignments.

Have been here:
http://support.microsoft.com/defaul...pport/kb/articles/Q51/9/78.ASP&NoWebContent=1

Some of my drives are ntfs don't show up in dos
so I am still am not certain about this configuration:

One 30 gb Maxtor eide drive: 1 primary inactive partition and 1 logical
partition.
Two scsi drives each with a single active primary partition.

EIDE: primary, inactive / logical inactive
scsi 0 primary, active
scsi 1 primary, active

If I choose to boot from scsi drive in bios then scsi 0 becomes C drive.
What would be the order of the other 3 partitions if configured as above?

Can someone explain how to get:

scsi 0 = C primary, active
scsi 1 = D
eide = E and F

and this:

scsi0 = C primary, active
eide = D
eide = E
scsi1 = F

Thanks to all,

Ken

 

[Overlord]

You are no doubt aware that DOS does not see nor access NTFS drives.
Half my drives are NTFS, half FAT32. When I boot do DOS I can access
4 drives as opposed to 8. I understand there is at least one
driver/util that will let you access your NTFS drives from DOS.

In Win2K, your drive letters are whatever you say they are.
Bring up Admin Tools ~ drive management, right click on the drive and
you should see options to change the drive letter. You can
temporarily change the D drive to W drive to free up the D letter for
a different drive, say E drive to be changed to D drive. Then change
the W drive to E drive. For example my CDROM is P drive, for Plextor.
My CDRW is R drive for Rewritable.

I have no IDE drives so cannot comment on their default designations.

Question about drive letter assignments.

Have been here:
http://support.microsoft.com/defaul...pport/kb/articles/Q51/9/78.ASP&NoWebContent=1

Some of my drives are ntfs don't show up in dos
so I am still am not certain about this configuration:

One 30 gb Maxtor eide drive: 1 primary inactive partition and 1 logical
partition.
Two scsi drives each with a single active primary partition.

EIDE: primary, inactive / logical inactive
scsi 0 primary, active
scsi 1 primary, active

If I choose to boot from scsi drive in bios then scsi 0 becomes C drive.
What would be the order of the other 3 partitions if configured as above?

Can someone explain how to get:

scsi 0 = C primary, active
scsi 1 = D
eide = E and F

and this:

scsi0 = C primary, active
eide = D
eide = E
scsi1 = F

Thanks to all,

Ken

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[Wolf Kirchmeir]

Question about drive letter assignments.

The following applies to IDE drives. BIOS reports the partitions that it sees
as "primary" and "extended/logical" on HD0, HD1, etc. The OS uses this report
to assign drive letters. (Technically, it's a little different, but that's
the effect, and it's easier to understand.)

For DOS (and Win3.x, Win9x/ME, which are really versions of DOS, and can't
run without it), the order of assigning drive letters is as follows. The
example letters assume one partition of each type on each drive:

Primary partitions on drive 0 (C
Primary partitions on drive 1 (D
Logical drives in extended partitions on drive 0 (E
Logical drives in extended partitions on drive 1 (F
CD-ROM drives (G
External drives (H
"It's all rather confusing, really."

Win NT/2000/XP default to the same scheme, but you can change the drive
letter assignments in Disk Management.

As Overlord pointed out, DOS doesn't see all partitions. In fact, different
OSs will see different partitions, or see the same partition differently,
which can cause problems if you have multiple OSs, since that makes it
possible to inadvertently write to the wrong partition. (There's one more
wrinkle with DOS. In DOS, you can designate the "last drive letter." If you
have more partitions than are accommodated within the range you specify, the
ones outside that range won't be seen by DOS.)

BIOS will boot to the first bootable partition it finds in "boot order
sequence" as defined in its settings. This is how you can boot from a floppy
or CD even though you have a bootable partition on the HD - very important if
you need to repair the system installed on the HD.

Boot Managers are always the "first bootable partition" when installed,
regardless of where they reside on the HD. The "master boot record" takes
care of that. (A BM is actually a minimal OS whose only function is to run
the boot operation.)

BMs intercept the BIOS report, and generally do not pass on all the
information to the OS that's booted. This way, the C: (boot) drive for one OS
can be "hidden" from the other OS (which will also designate its boot drive
as C. This also guarantees that the subsequent drive letters will be in the
correct sequence, _if_ each OS sees them all, and _if_ you haven't reassigned
drive letters. If you have reassigned drive letters, and/or the different OSs
see don't all see the same partitions, then every time you change OSs the
drive letter assignments will be different.

Drive letters and drive letter sequence usually change when you add hardware.
For this reason, I label all drives (volumes) with descriptive names, so that
regardless of drive letter, I can tell which is which. The descriptive names
will show in My Computer or its equivalent in other OSs.

IMO, drive letters are a legacy we can do without. All volumes should be
labelled; it should be easy to devise a simple scheme as default. Eg, every
OS could label its boot volume as "OS System." I see no reason why volume
labels shouldn't be visible to all OSs you happen to have installed. But
that's another issue.

HTH

 

[Bob I]

I don't have the oportunity to test this but,

Make the Only partition on the EIDE an Extended partition and split it
into two logicals D and E

If there is a Primary partition on the primary or secondary EIDE header
it will be seen before the SCSI header.

 

[GWHSU]

Bob,

Thats what I plan to try, I just wanted to get a clearer idea. I want to
remove an IDE drive that I am booting from (no OS), and add two scsi
drives. I'm having trouble because the IDE drive that I will keep
was the D and F drives, the D drive containing the OS. I'd like to
migrate the OS to one of the scsi and boot from the other scsi
leaving the IDE as E and F.