device mapper scrambles drive order - SOLVED

[Moriah]

I love the device mapper, and all the great things it does, but I am now working with my first hot-swappable machine, and it has 5 SATA hot-swappable slots. One of these, the left-most slot, is the boot device, so it always comes up as /dev/sda, but the other drives only come up as sdb thru sde if they are fully populated at boot. If a drive is missing at boot time, that slot is simply ignored and the next populated slot gets assigned the next available drive identifier. This can get extremely confusing.

To further complicate matters, if I pull a drive and then repopulate as a hot swap operation, assuming that all other slots are populated, it maintains its former drive identifier, but if I pull multiple drives then repopulate them in a different order, all the drive identifiers seem to get allocated on a lexicographically first identifier gets allocated first basis, which means there is no reliable correlation between drive identifiers -- like /dev/sda, dev/sdb, etc. -- and actual physical positions in the hot swap chassis.

In order to make this workable, especially for non-technical people, I need a way to tell the operator to remove or insert a drive into or from a particular physically identifiable position in the chassis.

How do I anchor the drive identifiers and permanently associate them with a particular physical slot?

Is there any way to physically blink the drive select led at a controlled rate without actually doing anything to the drive itself? This would make it easier for the operator to determine which slot needed attention. I realize this might be difficult to do if the slot is empty.

As a side question, how can I label the drives themselves (not the physical slots) so that the label is machine readable? I know there is a way to do this, but its been so long since I have used this feature that I forget how it works. Some of these drives will be part of a RAID. The XFS filesystem will be the principle filesystem in use, but it must also be able to handle other filesystems, so the label needs to be associated with the physical disk drive, along with the partitioning information, not with the filesystem.

Thanks for any help!
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[gentoo_ram]

You should be able to do this with udev, I would think.

Try:

[Moriah]

The /dev/disk/by-path directory was just what I needed.

Thanks!
_________________
The MyWord KJV Bible tool is at http://www.elilabs.com/~myword

Foghorn Leghorn is a Warner Bros. cartoon character.