Messages in this thread | | | Subject | Re: Volume management on Linux with the ext2fs. | From | Nicolai Langfeldt <> | Date | 04 May 1997 15:07:57 +0200 |
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scott@laird.com (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 out.
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. -- Nicolai
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