Fw: mkraid failure

[Kyriakos Ginis]

On Fri, 2 Mar 2001 15:14:28 +0200, Mihalis Tsoukalos wrote:
>
>Το πρόβλημά μου ακόμα παραμένει ότι αν και οι δύο δίσκοι είναι ακριβώς οι
>ίδιοι, το fdisk δείχνει διαφορετικά νούμερα στην γεωμετρία τους και έτσι δεν
>μπορώ να φτιάξω partition με το ίδιο μέγεθος:
>
>eugenia:/usr/share/doc/packages/raidtool # fdisk -l
>
>Disk /dev/hda: 255 heads, 63 sectors, 3737 cylinders
>Units = cylinders of 16065 * 512 bytes
>...
>
>Disk /dev/hdc: 16 heads, 63 sectors, 59560 cylinders
>Units = cylinders of 1008 * 512 bytes
>...

Από το Large-Disk-HOWTO:


  14.2.  Nonproblem: Identical disks have different geometry?

  `I have two identical 10 GB IBM disks. However, fdisk gives different
  sizes for them. Look:


       # fdisk -l /dev/hdb
       Disk /dev/hdb: 255 heads, 63 sectors, 1232 cylinders             
       Units = cylinders of 16065 * 512 bytes              

          Device Boot  Start      End   Blocks   Id  System
       /dev/hdb1           1     1232  9896008+  83  Linux native
       # fdisk -l /dev/hdd
       Disk /dev/hdd: 16 heads, 63 sectors, 19650 cylinders
       Units = cylinders of 1008 * 512 bytes

          Device Boot  Start      End   Blocks   Id  System
       /dev/hdd1           1    19650  9903568+  83  Linux native



  How come?'

  What is happening here? Well, first of all these drives really are
  10gig: hdb has size 255*63*1232*512 = 10133544960, and hdd has size  
  16*63*19650*512 = 10141286400, so, nothing is wrong and the kernel   
  sees both as 10.1 GB.  Why the difference in size? That is because the
  kernel gets data for the first two IDE disks from the BIOS, and the
  BIOS has remapped hdb to have 255 heads (and 16*19650/255=1232
  cylinders).  The rounding down here costs almost 8 MB.

  If you would like to remap hdd in the same way, give the kernel boot
  parameters `hdd=1232,255,63'.