Replace RAID Card, Use same RAID 1 Drvices, New Mobo

I have a Dell Poweredge 840 running SBS 2003 that has provided good service since mid-2007.  I have been thinking about buying a stripped Poweredge 840 on Ebay with the same processor specs on the presumption that it is probably the same MB and chipset as I have now. The object would be that if there is a system failure on the in-service unit, I simply pull the hard disks, put them in the new box (which has the same model RAID card) plug in the RAM, and then boot.

1. What is the likelihood that everything will work just peachy from the get go? I guess I'd try booting to the old RAID card first, but would it boot to a different but same model card with the RAID 1 drives from the other box?

2. I maintain a running Acronis image backup using universal restore of the in production unit. If plan A is not likely to work, how about if created a new RAID 1 Array on the spare unit, then restored the image. The drivers should all be the same. All is well with the world?

Thanks for your responses.
Smasher999Asked:
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jamietonerCommented:
I've done this before many times usually without issue. But having a good backup is essential
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PowerEdgeTechIT ConsultantCommented:
Neither option should give you any problems:

1.  If you put the drives from server 1 into server 2, without swapping the controller, the controller in server 2 will tell you that it found a new configuration (labeled 'foreign').  You need to Import the Foreign Configuration, then everything should work ok.

There is a chance that the two controllers will have older/newer firmware, which can cause problems, but it isn't likely to.

Simply moving the card with the drives should address both issues.  

If the controllers are different (newer 840's shipped with the PERC 6/SAS 6, and the older 840's shipped with the PERC 5/SAS 5), let me know before doing anything.

2.  Restoring from backup, as long as firmware is reasonably close or the same, should be fine, as they do use the same hardware.  BIOS versions may play a role as well, so check those before proceeding.
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DavidPresidentCommented:
Since you have a 2-Disk configuration, then you are insured that you will have a majority quorum, which in raid-firmware-developer jargon, even if the controller has an old configuration, that only counts as one vote, and the two disks in the RAID1 count as two, so the 2 disks will win.

HOWEVER ...
To insure there are no problems, you need to first fire up the new motherboard with NO disks attached ..

1. Then do a clear configuration from the BIOS.
2. Check out the BIOS/FIRMWARE revisions, then update them if they are not current.

Reason is that the metadata on the HDDs are upwards compatible when it comes to foreign drives, but not downward compatible. So by flashing latest firmware on new system, and blowing away any old config, then unless you have one of those act-of-God issues like losing RAM or the controller at exactly the wrong time, you have 99.99% probability of success.

(By doing #1 and #2, you are actually even going to be OK if one of the 2 disks decides to die.  That is because clearing the old configuration takes away one of the "votes" so then even if a drive dies, the metadata count of 1 on the surviving disk overrides the vote of now 0 on the controller.
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Smasher999Author Commented:
The old and new RAID controllers are both SAS 5/IR, but Dell uses two different model numbers for them. The model number on the in service unit is UCS-51. The standby unit is UN939. From all other indications, the cards themselves are idential in that both run on the same driver.

Any importance?

Thanks
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DavidPresidentCommented:
You will be OK, that model of controller (which is a LSI controller, BTW), handles foreign imports just fine, but do upgrade firmware  & BIOS (of the controller, not the motherboard, but upgrading motherboard always good idea) before attempting to import.
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PowerEdgeTechIT ConsultantCommented:
They are both SAS 5/iR cards, but Dell has multiple part numbers, reflecting when and where they were manufactured, so there may be a difference in firmware ... as dlethe said, updating them both to the latest (if possible - or at least to the same) version would be recommended.  Also, as dlethe advised, updating the BIOS and ESM (if older than the original) would also be a good idea, as support for devices can vary from one BIOS/ESM version to another.
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