libata equivalent for hdX=remap63

libata equivalent for hdX=remap63

[Alexander E. Patrakov]

Hello,

sorry if this is a FAQ, but googling for "libata remap63" gives nothing 
useful.

Some old computers need software like "Ontrack Disk Manager" in order to 
see large disks in the other OS. The way to deal with such setup in 
Linux was to add "hdX=remap63" to the kernel arguments. However, I 
cannot find the equivalent of this option in the new libata-based 
drivers. Could you please show how to migrate such systems to libata 
without removing the disk manager?

-- 
Alexander E. Patrakov
(not subscribed to linux-ide, please CC: on replies)

Re: libata equivalent for hdX=remap63

[Alan Cox]

On Sun, 02 Sep 2007 14:26:29 +0600
"Alexander E. Patrakov" <patrakov@ums.usu.ru> wrote:

> Hello,
> 
> sorry if this is a FAQ, but googling for "libata remap63" gives nothing 
> useful.
> 
> Some old computers need software like "Ontrack Disk Manager" in order to 
> see large disks in the other OS. The way to deal with such setup in 
> Linux was to add "hdX=remap63" to the kernel arguments. However, I 
> cannot find the equivalent of this option in the new libata-based 
> drivers. Could you please show how to migrate such systems to libata 
> without removing the disk manager?

The remap63 hack is ancient. Since the kernel acquired device mapper its
also unneccessary as you can use device mapper to set up a 63 sector
offset volume.

I'm amazed anyone is still using it but the right way to handle it on a
vaguely modern system isn't more kernel hacks but to teach dmraid to
handle it. If you've got an example of what the layout looks like
(especially if there is a way to autodetect it) then talk to Heinz (cc'd)
about getting it added to dmraid.

Alan

Re: libata equivalent for hdX=remap63

[Alexander E. Patrakov]

Alan Cox wrote:
> On Sun, 02 Sep 2007 14:26:29 +0600
> "Alexander E. Patrakov" <patrakov@ums.usu.ru> wrote:
>
>   
>> Hello,
>>
>> sorry if this is a FAQ, but googling for "libata remap63" gives nothing 
>> useful.
>>
>> Some old computers need software like "Ontrack Disk Manager" in order to 
>> see large disks in the other OS. The way to deal with such setup in 
>> Linux was to add "hdX=remap63" to the kernel arguments. However, I 
>> cannot find the equivalent of this option in the new libata-based 
>> drivers. Could you please show how to migrate such systems to libata 
>> without removing the disk manager?
>>     
>
> The remap63 hack is ancient. Since the kernel acquired device mapper its
> also unneccessary as you can use device mapper to set up a 63 sector
> offset volume.
>
> I'm amazed anyone is still using it but the right way to handle it on a
> vaguely modern system isn't more kernel hacks but to teach dmraid to
> handle it. If you've got an example of what the layout looks like
> (especially if there is a way to autodetect it) then talk to Heinz (cc'd)
> about getting it added to dmraid.
>   

Thanks Alan,

this is actually not my system, but a system of a user of my Live CD. I 
already asked him to mail me the first megabyte of his hard disk, but 
let me wait 24 hours for a reply. Would this information be enough for 
adding support for this into dmraid?

As for autodetection, I am really not sure. The user says that kernels 
prior to 2.5.70 had this autodetection built-in.

-- 
Alexander E. Patrakov

Re: libata equivalent for hdX=remap63

[Alexander E. Patrakov]

Alan Cox wrote:
> The remap63 hack is ancient. Since the kernel acquired device mapper its
> also unneccessary as you can use device mapper to set up a 63 sector
> offset volume.
>
> I'm amazed anyone is still using it but the right way to handle it on a
> vaguely modern system isn't more kernel hacks but to teach dmraid to
> handle it. If you've got an example of what the layout looks like
> (especially if there is a way to autodetect it) then talk to Heinz (cc'd)
> about getting it added to dmraid.
>   

I got no useful reply to my request for the user to send the first 
megabyte of the hard disk. However, using a cracked version of Hitachi 
OEM variant of OnTrack Disk Manager, I produced a 64GB qemu disk image 
with this disk manager, Windows 98 and a Linux partition (just in case). 
It works fine with hda=remap63 and thus serves the purpose of being an 
example of the layout.

The first 64 KB of this hard disk can be found at 
http://ums.usu.ru/~patrakov/first-64-kb.dsk (please tell me when I can 
remove this file).

The full disk image (obviously, without Windows 98 - but you can install 
it yourself) can be reconstructed as:

dd if=/dev/null of=first-64-kb.dsk bs=1M seek=65536

Note that you can't just reinterpret the OnTrackDM6 partition as a disk 
image because it doesn't start at sector 63. To use this image in qemu:

qemu -hda first-64-kb.dsk -hdachs 1024,16,63,none -cdrom 
your-favourite-livecd.iso

In the original image, I could do a "mount -t vfat -o loop,offset=64512 
/dev/hda /mnt" and see the Windows partition.

-- 
Alexander E. Patrakov

Re: libata equivalent for hdX=remap63

[Alan Cox]

> The first 64 KB of this hard disk can be found at 
> http://ums.usu.ru/~patrakov/first-64-kb.dsk (please tell me when I can 
> remove this file).

Thanks - it'll probably be after the kernel summit before anything
happens but the general question of using device mapper for this has been
raised there and looks a promising approach.