Question : Problem: Change Raid controller & keep raid intact?

Hi All,

    I realize the actual answer is "it depends".  However I am looking for a general pattern.  What I am concerned about is creating a RAID array (1 or 5, etc.) and having trouble with a faulty controller down the line.  I can pick up a promise raid card or even use a smart-array on an HP/Compaq.

   What I'm wondering is what happens when you go to replace a component like this?  Do you replace the card, reconfigure a raid with dummy drives?  Can you swap an existing raid "pair" (for example) and pull the drives and plant them onto another server?  Some have said that the raid info is kept on either the controller, the drives, or both.  I don't have a lot of equipment to experiment with, but I am looking for, again, patterns.  I'm happy to clarify if need be.

Thanks,
-A

Answer : Problem: Change Raid controller & keep raid intact?

With lower end cards like Promise, I think all information is kept on the drives. If you switch the controller, the data is gone, even if you reconfigure it with "dummy drives". On higher end cards like Dell's PERC controller or the HP Smart Array controller keep data on both the drives and controller. If the controller fails, and is replaced, when you reboot the server it comes up and says something to the effect of a configuration mis-match. You then have a choice of using the configuration on the drives or the controller. This is the best option. On a Dell, I have successfully moved a 6 disk drive, RAID 5 to a different, identical model server (the drives must be put back in the same order), and successfully brought the server up and accessed the data.