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    SubjectRe: [Possibly OT] Re: /proc/scsi/map
    On Mon, Jun 17, 2002 at 10:24:40PM -0500, Austin Gonyou wrote:
    > Taking a bit of an example from Veritas, would it be, at all, feasible
    > if n+ blocks were used at the end of the disk or partition(beginning
    > maybe?), to write a specific identifier that is unique to a specific
    > controller, or to make note of the drive serial number and store that on
    > the disk somewhere in some agreed upon understood way.

    Both LVM and the md code already do this. Ext2 and ext3 also have volume
    labels that can be used for this purpose. As much as I hate to admit it,
    this is the one area where I think MicroSoft did the right thing and
    snagged an unused byte in the partition table to mark the disks ordering
    (although we would need more than one byte). By putting it in the
    partition table, it would only need to be dealt with by one area of code
    (the partition reading code), would work for all filesystems, would work
    for all LVM and md types of code, and would be universal on linux systems
    and provide consistent, persistent device naming. Of course, if a disk
    dies and you put a new one in, then you have to rename the new disk to the
    old disks names when you partition it, but you would have to do that or
    something similar to that with all such possible solutions.

    The simple fact of the matter is that to provide truly consistent,
    persistent device naming requires that the naming be "end-to-end". You
    can not rely on *any* ordering issues (such as controllers, PCI busses,
    devices, etc), you have to read the name from the device itself and the
    name has to be totally irrespective of the devices current location on
    whatever bus it uses.

    --
    Doug Ledford <dledford@redhat.com> 919-754-3700 x44233
    Red Hat, Inc.
    1801 Varsity Dr.
    Raleigh, NC 27606

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