msdos and geometry of HD

These are tough questions:

1. Does a HD need a small msdos partition in order to keep the geometry of its partitions correct?

2. If yes, then if a HD which doesn't have it and has many other OSes(freebsd, linux...) and may have a wrong geometry(but works fine anyway). If now, I add a small msdos partition, will it mess up the(wrong) geometry?

 

The only OS I can remember that required a small DOS partition to function properly was NT running on a DEC Alpha chip.

If a MS-DOS partition were required, then the operating systems that pre-dated MS-DOS (like VAX, Unix, BTOS, etc.) would have been in big trouble.

What makes you think you have "bad geometry "?

 

re: bad geometry

No, I didn't say that the geometry was REALLY bad. But diffefrent partition managers may see the geometry a different ways WITHOUT the msdos partion.

 

mbr

May you are thinking Master Boot Record here? The MBR is the record keeper on the first sectors of hard drive, cannt 'member how many mb tho, & the old msdos.sys went arm-n-arm. Hey how do we live without that stuff anymore NEWT

 

re: mbr

Rancher. Yes, that what I meant. But then it comes to my second question in my original post, What will happen IF I add a small msdos partition to a HD that has many OSes ( but not windows )?

And answer to NEWT: this HD was found to have incorrect geometry by PM. but you know PM is MS oriented. And I can't say that the geometry is really incorrect, since all the OSes is running remarkably well.

 

Depending on where on the drive, and you are not trying to exceed the four Primary partitions/drives limitation, it can work.

If PM suggests your drive geometry is incorrect and offers to repair it, DECLINE!.

 

MBR

I would also beware of Power Quest offer to repair the partition. PM likes to do things its way or no way & I have found they are wrong more then not on this issue. PQM 7 here.

Put your Dos part before cyl 1024 & it should work ok

 

re: geometry

>If PM suggests your drive geometry is incorrect and offers to repair it, DECLINE!

I found that out the hard way!

>it can work.

What do you mean? it will correct the geometry the MS way or it won't hurt but won't do anything?

 

If it helps you to think of drives in terms of geometry, (I tend not to, they either are or are not, usable drives), and PM is telling you there is a geometry problem then you obviously choose to believe what PM is telling you. This now brings you back to where you started, so if you want to create a DOS partition, all the parameters have been defined within this thread, just do it!

 

Rancher - the MBR uses most of the 512 BYTE first sector of the drive. 446 bytes I think for the actual master boot record and the remaining space is taken up by some other odds & ends.

 

Also, if you are using a hard drive that requires a drive overlay and if for some reason the overlay doesn't load during the boot process PM will report geometry errors. Just thought I'd mention it thinking perhaps you had one and uninstalled it without updating your bios.

 

re: ge0metry

Different geometry didn't seem to affect *nix OSes but it may affect the boot loaders.

 

MBR

thx Newt

 

LBa32

For those who are interested in the subject and not entirely satisfied with the discussion so far, there is an article which talk about it at lenght:

http://www.win.tue.nl/~aeb/linux/Large-Disk.html#toc5