harddisc has not 63 sectors per track

[Axel Wein]

Hi,

I wanted to partition an Advanced Format HDD with "geo ? 255 56" using DFSee. But if I try to install AIR-BOOT, I get the message "AiR-BOOT is unable to install. Your harddisc does not have at least 63 sectors per track". First attempt was with v 1.1.0, second with the original 1.06. So I think all versions are affected.

Best regards,
Axel Wein

[Ben Rietbroek]

Replying to agw:

Hi,

I wanted to partition an Advanced Format HDD with "geo ? 255 56" using DFSee. But if I try to install AIR-BOOT, I get the message "AiR-BOOT is unable to install. Your harddisc does not have at least 63 sectors per track". First attempt was with v 1.1.0, second with the original 1.06. So I think all versions are affected.

Best regards,
Axel Wein

Hi Axel,

This is not a bug but a requirement of AiR-BOOT.
It's size is 31744 bytes which constitutes 62 sectors of 512 bytes.
The last sector (63) is used by eComStation to store LVM information.

Almost all harddisks use 63 sectors per track.
Why would you want to have this 'alien' geometry anyway ?

The manual states this requirement of 63 sectors per track by the way.

Regards,

Ben.

[Axel Wein]

Hi Ben,

of course you are right, this requirement is in the manual. By the way my appreciation for the manual and all your work on AiR-BOOT.

I wanted that geometry to get an aligned Advanced Format HDD with 500 GB. Jan van Wijk (DFSee) wrote, I could do it this way. But as it seems, there is another problem, I can't put an 1 MiB offset in front of the partitions, this is mandatory for Advanced Format HDDs. The offset gets always 6.9 MiB.

So I have to give up - and use the HDD misaligned.

Thank you
Axel Wein

[Ben Rietbroek]

Replying to agw:

Hi Ben,

of course you are right, this requirement is in the manual. By the way my appreciation for the manual and all your work on AiR-BOOT.

I wanted that geometry to get an aligned Advanced Format HDD with 500 GB. Jan van Wijk (DFSee) wrote, I could do it this way. But as it seems, there is another problem, I can't put an 1 MiB offset in front of the partitions, this is mandatory for Advanced Format HDDs. The offset gets always 6.9 MiB.

So I have to give up - and use the HDD misaligned.

Thank you
Axel Wein

Hi Axel,
(Thanks :-)

Advanced Format is only interesting if your harddisk truly has a physical sector size
of 4096 bytes or larger. Then a performance gain is acquired because 4kB alignment of
partitions and filesystems cause the blocking and deblocking not to span 4kB boundaries.

The 4kB physical size is normally used with todays very largs disks.
Since you mention your harddisk is 500GB I doubt if it's physical sector size is
larger than 512 bytes, so an Advanced Format layout would not make any difference.
(Unless the specs of your 500GB harddisk state it uses >512 byte physical sectors)

Anyway, the Advanced Format layout is coupled to the new MiB Partitioning Scheme, where partitions
are allocated on MiB boundaries and are of n * MiB size.
Since the Logical Volume Manager of eComStation uses CHS, and requires CHS alignment,
it will bark at most MiB layouts. This is because most MiB boundaries do not map on CHS boundaries.

Theoretically it's possible to create an Advanced Format MiB layout where the boundaries coincide
with CHS boundaries, but that requires 'alien' CHS geometries, mostly with an even number of sectors
per track. (Multiple of 4kB) The 56 SPT constitutes of 7 4kB blocks, 64 SPT would be the next value and would constitute 8 4kB blocks. So a geometry of ? ? 64 is more compatible with MiB partitioning.

However, such a geometry is not CHS-standard and eCS LVM might not like it.
You would have to experiment with it.

The reason you get 6.9 MiB for the offset is because DFSee aligns on CHS by default when used
under eComStation I guess. So you would have to change some option to let it align on MiB.
Which thus may wreck havoc with eCS LVM if there is not a 'compatible' CHS geometry in the
LVM info-sectors. You could also use a Linux Live CD and use GPartEd to create partitions
on an MiB boundary. Then use DFSee to generate default LVM info for them.
(But eCS LVM might still bark...)

All the above is of no interest if the physical sector size of your 500GB disk is 512 bytes.
If you go experimenting with eCS and an MiB compatible geometry using the above info,
then be prepared for strange things.

Regards,

Ben.

[Axel Wein]

Hi Ben,

yes the physical sector size of my HDD is really 4096 bytes! I didn't know anything about Advanced Format as I bought this harddisc. With eCS I don't feel a difference, but Win XP is terrible slow under certain circumstances, since I cloned it to this HDD. Several attempts with GParted and DFSee were unsuccessful. So I won't make further experiments. The only thing I will try, is not to clone, but to backup and restore the data to the new drive. I read, that cloning to a misaligned HDD should be very bad.

Thank you very much for your help and the above infos about Advanced Format layout.

Best regards,
Axel Wein