dual disks, two boot.ini, which boot.ini

October 23, 2011 at 16:09:11
Specs: Windows XP, intel/1 Mb
I have a system with four internal hard disks. two of those hard disks have their own operating system (one is a clone of the other so that if a catastrophe occurs, I can immediately boot from the clone.

the question is which boot.ini is run by the ntldr. Don't say "C:\" This is WHY:

if i set the default operating system to be located on r(0)p(1), then the partitions are labeled
c:\ g:\ h:\ etc....on the default operating system disk

If i select the other disk (r(1)p(1) as the operating system I wish to run, then the partitions are labeled c:\ g: g:\ etc on this second disk and the original default operating disk is now labeled with different letters (ie: d:\ m:\ etc)

so it is clear that the bios determines which physical disk is the starting point. So I want to know which disk is selected and why.

I am guessing that the bios selects the disk which has an MBR and is selected as "active"
But the problem with that is when I clone, both disks seem to have an MBR and both appear to be active.

Perhaps the bios always chooses Sata 0 as the first disk to find an MBR and an active flag
and if it does not find it, then the bios may go to Sata 1?

Any insight would be appreciated.

oh by the way, am i right in thinking that if my default physical disk crashes, then i must ensure that the clone application clones the boot.ini and the MBR data on the cloned disk
so that the bios will, indeed, find a boot.ini and MBR to load.



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October 23, 2011 at 16:37:38
The BIOS goes to each bootable device in the boot order until it find a device that is bootable. If it is booting windows it will use the boot.ini that is in the root folder of the first primary partition of the disk it is booting from. This may or may not be drive C: - it depends on the configuration at the time of the installation of the OS.

From Windows XP onwards there is no absolute requirement for the boot and system files to be on drive C:. The only absolute requirement is that the System and Boot files be on a primary partition. At this stage of the boot process drive letter do not exist as it is not until the NTloader finds the Operating System that the OS starts allocating drive letters. The boot and system drives will get the same drive letters every time but they could be anything.

Every hard dsik that is partitioned has an MBR. It is different for a bootable hard disk and a non-bootable hard disk as a bootable one contains the boot loader which a non-bootable disk does not. The boot loader is put there during the OS installation process. and is the very first thing the BIOS reads of the hard disk during the boot process. Once the boot loader is loaded into memory control is handed over to it and it then continues with boot process looking for the System files, NTDetect,com, NTLDR and Boot.ini .


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