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HP MS2A2012I SAN Question - Controller failure, Data loss or not?

Posted on 2010-11-24
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Last Modified: 2012-05-10
Hi,

I'm just looking for some clarification on what happens in the event of a controller failure on a SAN. Our outsourced IT  recently had an issue with a HP SAN where the controller failed and as there was no secondary controller,  they had to order a part and then restore the unit. The Outsource company is recommending we buy a second controller as we have the same model as one that they had issues with. All our VM's reside on this controller, there are weekly full VM backups to another physical machine.

Just wondering if the data is always safe in this event as they are saying the data is safe. Is this correct? How is the info stored on the disks? I'm not a storage specialist so would like advice from those who are.

Cheers
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Question by:afi99
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Wolfhere earned 125 total points
ID: 34210309
As long as the backed up data is stored "off site", you are pretty safe. Its just a matter of having redundancy on hardware. Pretty safe, but safer with the redundant controller. The data is not on the controller, it resides on the drives. Your SAN has HD redundancy but no controller redundancy. You would rather be safe than sorry...waiting on a replacement. Good call by your Outsource company
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by:afi99
ID: 34210496
Good call but a case of reactive planning rather then proactive, they sold the original SAN's without redundancy.

Sorry, I just need a little more clarification, if the backups fail  and we're relying on the SAN drives then no issue as long as we replace with the same controller?
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by:jakethecatuk
jakethecatuk earned 125 total points
ID: 34211186
as wolfhere has said, the data is on the drives and will always be on the drives.

if the controller fails and is replaced, the controller will look at the disks for the raid configuration in use on the array.  provided the controller is the same as the one that failed, then this process will work seemlessly and you shouldn't have any issues.

if your backups have failed as well, then again, provided you haven't suffered drive failure, your data should be safe but you are at risk.
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by:afi99
ID: 34211265
Thanks guys much appreciated
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by:SelfGovern
ID: 34214929
In fact, MSA supports upgrading to newer controllers without loss of data.   HP publishes white papers on the steps to take (what info you need to record in order to perform a smooth controller upgrade) -- it turns out that the same information you'd capture to do an upgrade would be required for a replacement due to failed HW... so it may be worthwhile to go to www.hp.com/go/p2000 , download the upgrade white papers, and make sure you've got the necessary information recorded and saved securely.

(In a rebranding effort, the MSA is now the P2000 MSA, starting with the 3rd generation of the product)
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