Andries Brouwer wrote:
>
>That shortens our conversation to
>
>Stephen: There is no place to put an UUID.
>Andries: Use a Linux-type partition table.
>Stephen: It is better to use Linux logical volumes.
>
>That is a reasonable point of view.
>(I disagree a bit, mostly because it is the wrong "level"
>to put such information. It means that the code that decides
>whether a disk has a certain volume label has to understand
>all partitioning schemes in existence, and dig in the partition
>table to find where LVM lives and then look there to find
>a disk label.)
Not necessarily. The LVMS Architecture from IBM has several abstraction
layers. By the time the LVMS needs to begin looking for labels and LVM
data, it is working with logical partitions. All logical partitions are
the same and are accessed the same, so that the code dealing with volume
lables and volume construction does not have to worry about the
partitioning scheme in use or even the device that the partition lies on.
As for the code handling the partitioning, that code is isolated into
plug-in partition management modules. This allows the LVMS to be updated
to deal with new partitioning schemes by the addition of a plug-in module
for each new scheme. Devices are abstracted in a similar fashion (Logical
Disks). Even the features that can be applied to logical partitions when
creating logical volumes (RAID 0, RAID 5, Drive Linking, Encryption,
Mirroring, etc.) are isolated into plug-in modules.
Getting back to the problem at hand, while using the LVMS to store a
UUID/volume label/etc. works for logical volumes, it does nothing for case
where Linux must share a partition with another operating system. Assuming
that the other operating system does not understand Linux logical volumes,
we have a case where the LVMS can not necessarily be used to store a
UUID/volume label within the partition. OS/2 solved this by using the DLAT
stored in an unused sector following an MBR or EBR. This solution is not
necessarily portable to other partitioning schemes, but is a single "one
size fits all" solution required (or even possible)? How does one
associate a volume label/UUID with a partition when the partition is to be
shared with another OS?
Regards
Ben Rafanello
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