What determines hard disk number?

[Frragrant]

I need some help to figure out how the OS gives a number to the internal hard drive. I am using Acronis Drive Image to create a recovery of my entire system. I had installed a two OS in two different partition. There is a 320GB hard drive in my computer. And there are 3 more partitions. Now when I try to restore I found that the drive number is being changed. I found in the Linux. The drive which was set as 1 is no set as 0. Is this is a problem.

[Taksal]

That is done by the mbr I think. It is commonly noticed in linux system on boot you can see the drives and the partitions are marked in numbers. It is giving as 0 / 1 and so on. You must not make any changes to this. And when you restore your system sometime the drive numbers are changed. It does not put any effect on your system.

[stringse]

According to me this is done by the bios. But I am not sure. Each connectors on the board has a set of numbers. Like for IDE it is separate for Sata it is different. On that basis the drives are configured. Many tools allows you options to modify the same but somehow it is not recommended to test it.