[CentOS] Controlling the order of /dev/sdX devices?

Fri Apr 1 14:04:04 UTC 2011
Cal Sawyer <Cal.Sawyer at artsalliancemedia.com>

I think that everyone lese lives in a far more ordered universe than i
do.  My "problem" - no, wait - "challenge" is that i have zero control
over the origin of incoming media on USB and eSATA.  Could be any brand
of USB stick sold under the sun or HDDs formatted FAT32, NTFS, ext2/3.
The only constants are things i directly control (sysdisk, RAID) -
everything else is a crap-shoot.  Everyone else can use labels.

I don't know about you but it "feels" like mounting a RAID array,
possibly with an active mySQL database on it under udev is kind of
disaster-prone.  I would much rather mount via fstab.

- csawyer

-----Original Message-----
From: centos-bounces at centos.org [mailto:centos-bounces at centos.org] On
Behalf Of Brunner, Brian T.
Sent: 01 April 2011 14:51
To: CentOS mailing list
Subject: Re: [CentOS] Controlling the order of /dev/sdX devices?

centos-bounces at centos.org wrote:
> Nope sir.  Assume never the same device twice and no control
> over those devices, so UUID is out of the question.

UUID is out of the question where I have 3 drives (main and two backup)
with "wear leveling" wherein ANY of the drives, put in /dev/sda's
position, is the boot drive, the identical backup on /dev/sdb will get
backed-up-to on a daily basis, and on a weekly basis the drive in
/dev/sdb moves to /dev/sda's connector (becoming the boot drive),
'/dev/sda' goes off-site, and the third moves to /dev/sdb's position
(and gets backed-up-onto promptly.

LABEL also fails here.

> Yes, that's why you assign a LABEL to the device :) If the
> same hard drive gets used on the same server, but on random
> ports every time then the LABEL will still stay the same. I
> have a similar setup where I mount about 40-odd USB drives to
> a server on a regular basis. They each have their own mount
> points in /mnt/usb-hdd/xxxxxxxxxx and irrespective of which
> drive I connect to which USB port, or on which order, they
> all get mounted where they're supposed to :)

This is excellent where each drive has distinct content.

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