[gPXE] Change drive number of the iscsi boot drive?

[Binh Thai]

Hi Shao,

 

Thanks for your reply.

 

I forgot to mention that I meant "drive 0" in the context of Windows
disk drive numbering. My goal is to boot a system from an iscsi target
without disrupting the disk drive numbers of the internal hard drives.
For example, if I have one internal hard drive, I want to see it
detected as Disk 0 whether I boot from it or from the iscsi target. If I
boot from the iSCSI target, I want to see the iscsi target as drive 1,
not 0. Currently, the iSCSI drive would become Disk 0 and push the
internal drive to Disk 1.

 

I think the PnP enumeration process in Windows has some relationship
with the BIOS drive numbering. Could you please point me to some
in-depth documentation regarding the BIOS drive numbering and how int13
is used?

 

Thanks again,

Binh Kien Thai



 

From: Shao Miller [mailto:Shao.Miller at yrdsb.edu.on.ca] 
Sent: Tuesday, January 18, 2011 11:19 AM
To: Binh Thai
Cc: gpxe at etherboot.org
Subject: [SPAM] - Re: [gPXE] Change drive number of the iscsi boot
drive? - Email found in subject

 

On 1/18/2011 10:42, Binh Thai wrote: 

Hello Everyone,


Hello.





It seems by default the iscsi boot drive initiated from gPXE has the
drive number 0.


I think that you meant to type "BIOS drive 0x80" rather than "drive
number 0".  BIOS drive 0x00 would be the first floppy disk drive.




Is there any way to change this drive number to an arbitrary number? The
reason is I want to keep the drive order and numbers of the internal
hard drives intact.


If you wish to change the drive number away from 0x80, what are you
hoping to do with it?  Boot it?  I am under the impression that a lot of
HDD boot-loader code expects to be run from drive 0x80.

gPXE assigns a "natural" drive number to the SAN; the "natural" number
would be the next number available.  If you had 0x80 and 0x81 already,
then it would get 0x82.  But then gPXE swaps that with the real 0x80
just for booting purposes, since 0x80 is traditionally the booting HDD.
See gpxe/src/arch/i386/interface/pcbios/int13.c for some relevant source
code.

- Shao Miller

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