Re: Volume management on Linux with the ext2fs.

Nicolai Langfeldt (
04 May 1997 15:07:57 +0200 (Scott Laird) writes:
> That's a bit tricky. Add a header to each LV partition. Assign each
> LV volume a universally unique ID, and give each partition in the LV
> its own UUID and put the LV and partition UUIDs in the partition
> header. Now all you need is a partition UUID<->block offset mapping.
> For small LVs, you can store the complete mapping in the header. For
> larger LVs, you can let each partition keep track of a subset of the
> mappings (2 forward, 2 back, perhaps). When you reboot, a quick scan
> of all partitions on all drives will correctly identify which are
> involved in LVs, and the UUIDs should be enough to recreate the
> complete LV layout.

This would be good and work with dynamic SCSI devices as you point

Story: Once I was mounting two new SCSI disks in a AIX box. The other
disks were in the volume manager. I had some problems with the
SCSI-ID switches in the cabinet and by mistake renumbered the already
used drives. The macine was then powered to see if it would discover
the newly mounted drives or not _this_ time. It came up and the
filesystems were all OK even though the underlying SCSI devices were
completely renumbered. I only discovered the renumbering mistake once
I re-examined the ID switches because the new drives did _not_ come
up. I was quite impressed when I realized what had happened and how
well AIX had handled it.

DEC-UNIX would not handle such a case. Linux _must_ because of the
dynamic numbering scheme we use.