question on sfdisk geometry estimation

question on sfdisk geometry estimation

[Ulf Zibis]

Hi,

using sfdisk -l I had this output:

Disk /dev/sda: 19457 cylinders, 255 heads, 63 sectors/track
Units = cylinders of 8225280 bytes, blocks of 1024 bytes, counting from 0

    Device Boot Start     End   #cyls    #blocks   Id  System
/dev/sda1   *      0+   3038    3039-  24410736    7  HPFS/NTFS/exFAT
/dev/sda2      18936+  19456-    521-   4180680   12  Compaq diagnostics
/dev/sda3       3039    5390    2352   18892440   83  Linux
/dev/sda4       5391   18935   13545  108800212+   5  Extended
/dev/sda5       9725+  12764    3040-  24418768+   7  HPFS/NTFS/exFAT
/dev/sda6      12765+  18935    6171-  49568526    7  HPFS/NTFS/exFAT

Disk /dev/sdb: 10337 cylinders, 240 heads, 63 sectors/track
Units = cylinders of 7741440 bytes, blocks of 1024 bytes, counting from 0

    Device Boot Start     End   #cyls    #blocks   Id  System
/dev/sdb1   *      0+   4604-   4605-  34812823+   7  HPFS/NTFS/exFAT
/dev/sdb2       9782   10336     555    4195800   12  Compaq diagnostics
/dev/sdb3       5952    9781    3830   28954800    f  W95 Ext'd (LBA)
/dev/sdb4       4604+   5951-   1348-  10183680    7  HPFS/NTFS/exFAT
/dev/sdb5       5952+   9781    3830-  28954768+   b  W95 FAT32


So I'm wondering why sfdisk assumed sdb to be 240 head-aligned instead of 255.
All partitions except the sdb2 match with the 255*63 alignment.

Any hint, how the geometry should be estimated correctly?

Many thanks to your answer,

-Ulf

Re: question on sfdisk geometry estimation

[Ulf Zibis]

Oops,

by now *completely* converting output of sfdisk -d, I now can see, that I was mostly in error, see 
below ...

Am 27.11.2012 11:14, schrieb Ulf Zibis:
> Hi,
>
> using sfdisk -l I had this output:
>
>
> Disk /dev/sdb: 10337 cylinders, 240 heads, 63 sectors/track
> Units = cylinders of 7741440 bytes, blocks of 1024 bytes, counting from 0
>
>    Device Boot Start     End   #cyls    #blocks   Id  System
> /dev/sdb1   *      0+   4604-   4605-  34812823+   7 HPFS/NTFS/exFAT
> /dev/sdb2       9782   10336     555    4195800   12  Compaq diagnostics
> /dev/sdb3       5952    9781    3830   28954800    f  W95 Ext'd (LBA)
> /dev/sdb4       4604+   5951-   1348-  10183680    7 HPFS/NTFS/exFAT
> /dev/sdb5       5952+   9781    3830-  28954768+   b  W95 FAT32

# partition table of /dev/sdb
unit: sectors

/dev/sdb1 : start=       63, size= 69625647, Id= 7, bootable
/dev/sdb2 : start=147903840, size=  8391600, Id=12
/dev/sdb3 : start= 89994240, size= 57909600, Id= f
/dev/sdb4 : start= 69625856, size= 20367360, Id= 7
/dev/sdb5 : start= 89994303, size= 57909537, Id= b

unit: C/H/S - 10337.4 cylinders, 240 heads, 63 sectors/track

/dev/sdb1 : start=    0/1/0,    size= 4604/209/0, Id= 7, bootable
/dev/sdb2 : start= 9782/0/0,    size=  555/0/0,   Id=12
/dev/sdb3 : start= 5952/0/0,    size= 3830/0/0,   Id= f
/dev/sdb4 : start= 4604/212/20, size= 1347/11/27, Id= 7
/dev/sdb5 : start= 5952/1/0,    size= 3829/239/0, Id= b

unit: C/H/S - 9729.3 cylinders, 255 heads, 63 sectors/track

/dev/sdb1 : start=    0/0/63,  size= 4333/254/0,  Id= 7, bootable
/dev/sdb2 : start= 9206/150/0, size=  522/90/0,   Id=12
/dev/sdb3 : start= 5601/225/0, size= 3604/180/0,  Id= f
/dev/sdb4 : start= 4334/2/20,  size= 1267/206/27, Id= 7
/dev/sdb5 : start= 5601/226/0, size= 3604/179/0,  Id= b

Thanks,

-Ulf