[CentOS] Order of sata/sas raid cards

Fri Aug 24 14:49:23 UTC 2012
Les Mikesell <lesmikesell at gmail.com>

On Fri, Aug 24, 2012 at 9:24 AM,  <m.roth at 5-cent.us> wrote:
> > I'll step into this again: let's look at the context.
> 1. a drive's failed. No conflict.
> 2. a server's failed, and you want something off one of its disks:
>      a) you put it in a hot swap bay, and aren't rebooting the server -
>            you are going to be manually mounting it, so no conflict
>      b) you need to replace the server in -10 sec: you throw the drive(s)
>            into a standby box, and either
>           i. it's got partitions labelled /boot and /; fine, you
>               *want* it to use those
>           ii. you want a drive from another disk on that failed
>                system: no problem - see 2.a.
>      c) you have a system without hot swap bays, and you install
>           the drive from the failed system, and then you do have to
>           power up; this is the only case I can think of, off the
>           top of my head where you have a collision. In this case,
>           you need linux rescue, and relabel.
> So, where's the big issue with std. labels?

You power down, add some disks that you want to re-use.  Maybe even
add a controller.  Just because a bay looks like you can hot-swap
doesn't mean it is a good idea if you don't have to.   You boot up.
When the label scheme was first rolled out, the machine wouldn't boot
if it found a duplicate.   Now it will pick one.  Possibly the wrong
one.  As you might when you do a rescue boot for the relabel since you
won't know which controller is detected first.

  Les Mikesell
    lesmikesell at gmail.com