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Re: udev causing data loss?

On Sat, Nov 15, 2008 at 12:36:30PM -0600, lee wrote:
> On Sat, Nov 15, 2008 at 10:42:52AM -0700, ghe wrote:
> > At the time of my misadventure, I was still expecting sda to be the
> > lowest ID on the lowest SCSI bus -- there were no SATAs at the time, not
> > around here anyway.
> That is what I would expect. Are you saying that there is no way to
> tell which disk is which one from the device names?
> If that is true, how does the user, how does the system know which
> disk is which one? As user, I can eventually tell with fdisk -l and
> looking at the info --- *if* the disks are all different. But how does
> the system figure out if the device refered to in /etc/fstab is
> actually the device that should be refered to?

Lets say you have an old server with 12 disks on two scsi busses an
you're using mdadm (rather than a hardware raid card).  Lets say that
all 12 drives are in one array (just to make life interesting).  One of
those disks dies.  

mdadm would have assembed the array (before the failure) and you can get
a list of /dev/sd? devices that make up the array.  When a drive fails,
you get a message, presumably telling you that e.g. /dev/sde has failed.
How do you know which drive has failed so that you can swap it?


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