[Linux-HA] device mapping Raid1 problem if the first external storage off

Alan Robertson alanr at unix.sh
Tue Oct 18 14:05:51 MDT 2005

Robert Fehrenbach wrote:
> HI,
> we have a rh es3 server which has two qlogic qla2312 adapters installed. On
> each qla2312 adapter is one external data storage (msa1000). Every storage
> shall distribute scsi devices. The first (card0) shall always distribute
> /dev/sda devices and the second (card1) shall always distribute /dev/sdb.
> Now, if both storage systems are powered on then the device mapping is ok.
> But is the first storage powered off and a reboot performs. Then the first
> storage are not detected, only a message at loggin, that there is no volumes
> present. The boot process comes now to the second controller and detects
> volumes. But now the volumes/devices detected as /dev/sda. And this is an
> error, because for redundancy reasons there is a software mirror /dev/md0
> above the both external storages.
> The way for solution I think is a device mapping like controller 0 volume 0
> = /dev/sda1 and controller 1 volume 0 = /dev/sdb1.
> Do you have a way to show the solution. Maybe at the file sd.conf, if it
> possible.

I'm missing something in your description - I don't understand it.

In spite of not understanding your question, I'm pretty sure this is 
more of a straight RAID question than an HA question.

As a general rule, you need to NOT rely on device numbering if you're 
concerned about HA - and it's much worse on fiber channel.  Mounting by 
uuid or volume label is a much better idea.

     Alan Robertson <alanr at unix.sh>

"Openness is the foundation and preservative of friendship...  Let me 
claim from you at all times your undisguised opinions." - William 

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