SATA, Raid 1, LVM and controller question.

[Robin Laing]

Christofer C. Bell wrote:
> On 12/15/05, Robin Laing <Robin.Laing at drdc-rddc.gc.ca> wrote:
> 
  > Accepted practise is to run mirrors across controllers for reasons of
> performance (ie; avoding the situation you're seeing) and for fault
> tolerance (loss of a controller).  If you have a correctly configured
> /etc/mdadm.conf file, then you should (in theory) be able to simply
> plug the drive into the other controller and have it work.
> 
> The md subsystem does not look at, for lack of a better term, the
> "hardware path" of the drives it's assembling into an arry, it looks
> at the UUID that's tagged to each disk.  This UUID is unique per RAID
> volume regardless of where the disks are physically located in your
> machine.
> 
> You can see this UUID by running the following command:
> 
> # mdadm --detail --scan | grep ARRAY
> 
> In fact, you can put the output of that command in /etc/mdadm.conf and
> have a more or less working configuration.  You may choose to add
> "auto=md" at the end each line to force the md software to create the
> relavent md entries in /dev at boot time should they be found to not
> exist.
> 
> You'll also need to add the following two lines on top of each ARRAY entry:
> 
> DEVICE partitions
> MAILADDR root
> 
> The first line tells mdadm to use /proc/partitions when determining
> what it should scan for md plexes.  You can specifically enumerate
> partitions or devices here instead as outlined in the manpage for
> mdadm.conf.  The second line tells mdadm who to email should a plex in
> an md device fail or otherwise experience problems.
> 
> Best of luck!
> 
> --
> Chris
> 
> 

Chris,

Thank you for the information.  I will give it a try and see what 
happens.  md and lvm are both new to me.  I wish I had thought of this 
when I added the drives.

If it is that easy, I will be a very happy boy.  :)  But as we all 
know, there is something that will make that 5 minute job a 3 hour task.

Robin