Re: Hot Swap Disks

From: Keith Lofstrom (keithl_at_kl-ic.com)
Date: 01/20/04

  • Next message: Rui Miguel Seabra: "RE: Whitebox Linux" 
    To: fedora-list@redhat.com
Date: Tue, 20 Jan 2004 08:51:37 -0800

                                                                                    
    John Sutherland <fedora@sneeu.com> writes:
    > Is there anyway to turn off an IDE hard disk for hot swapping?

    Yes there is, but it is a bit of a kludge until a bug gets fixed.
    Alan Cox and others have written code that permits this, and the
    code is in the FC1 kernel.

    In theory, all you need to do is:

       unmount /dev/hdXXX # for all the partitions
       hdparm -b 0 /dev/hdX # for the whole drive

       # power down drive, swap, power up

       hdparm -b 1 /dev/hdX
       mount /dev/hdXXX /mntpoint # for all the partitions

    The "hdparm -b 0" command tristates the IDE controller lines so you
    can remove the drive without damaging the hardware. Of course, the
    drives should be in caddies so that the powerdown occurs properly.
    I like the Vipower cages for this.
       
    *** HOWEVER ***, there seems to be a bug in the process somewhere
    (see bugzilla.redhat.com #113693) that fails to upgrade the geometry
    tables for the drive. So, I end up doing this to restart the new drive:

       hdparm -b 1 /dev/hdX
       sfdisk /dev/hdX <control C> # !!!
       mount /dev/hdXXX /mntpoint # for all the partitions

    sfdisk seems to know enough to diddle the tables. This is risky,
    though; one wrong character typed into sfdisk and the drive is
    repartitioned. I would sure like a better technique, or else have
    the bug fixed.

    That said, I have done this dozens of times as part of my drive-to-drive
    backup scheme ( http://www.keithl.com/linuxbackup.html ) so if you are
    careful it should work until the bug gets fixed.

    Keith 

    -- 
Keith Lofstrom           keithl@ieee.org         Voice (503)-520-1993
KLIC --- Keith Lofstrom Integrated Circuits --- "Your Ideas in Silicon"
Design Contracting in Bipolar and CMOS - Analog, Digital, and Scan ICs
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