Re: 2.7 block ramblings (was Re: DMA for ide-scsi?)

Andre Hedrick
2003-09-15T03:41:18Z

Matt:

This would require the generic mapping of disc labels away from the
current hdX/sdX to hdN where 0 =< N < 5. This issue will be mapping EDDS
which you are working on, and I tip my hat for what value it has left.

I will chat offline more in details to see where you are going and if I
can offer help from the T13 side of life.

Cheers,

Andre Hedrick
LAD Storage Consulting Group

On Sat, 13 Sep 2003, Matt Domsch wrote:

> > Further, some sites may prefer block-level GUIDs to fs-level ones.
> > Sites using raw partitions instead of filesystems, for one.
>
> The EFI GUID Partition scheme (aka GPT aka CONFIG_EFI_PARTITION)
> stores a GUID in the disk label to define the whole disk, plus another
> per-partition GUID and per-partition label. So even if the file
> system doesn't have one, if you're using GPT, one *could* use those.
> I haven't hacked up mount to search for those though. If there's
> enough interest, I'll do so. Recall GPT is currently only used on
> ia64, though the code works fine on other arches including x86, and
> it's been decided (on l-k at least) that GPT will be the default disk
> label format for systems running 2.6.x kernels with disks >2TB, as the
> msdos label can't hold it.
>
> > The boot disk, OTOH, is tough. Right now, we just assume the
> > sysadmin knows what's he's doing, when he installs lilo or grub on a
> > disk. You care about the boot disk when installing lilo... maybe
> > there are similar situations too which I do not recall. As Alan
> > said, besides EDD (only on newer boxes) there's really nothing.
>
> EDD BIOSs are coming, slowly... 2 work today correctly, several more
> are "close but no cigar", it's all the rest that worry me.
>
> There's one more trick that's being used successfully, which I would
> like to add to the EDD code. That's "let BIOS help you out before
> installing". i.e. you boot into a FreeDOS environment, write a
> system-unique disk signature to the boot disk (int13 device 80h)
> "BOOT" or something - we've got 4 bytes available in the msdos label
> for it, then reboot and let Linux go grab the signature,
> store it, and like edd.o does, export it to userspace. Now from
> userspace one can see what Linux-named-disk has the signature you're
> looking for, and voila, you now solved it w/o needing EDD BIOSs. But
> it requires a non-Linux boot step somewhere in the install process.
>
> Thanks,
> Matt
>
> --
> Matt Domsch
> Sr. Software Engineer, Lead Engineer
> Dell Linux Solutions www.dell.com/linux
> Linux on Dell mailing lists @ http://lists.us.dell.com
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