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A whole iSCSI SAN failure ?

Posted on 2013-02-07
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Last Modified: 2013-02-09
Hi,

Have anyone experienced a whole SAN failure due by any reason ?
The general thinking is that "anything can fail" makes a person uncomfortable with
having everything in a single SAN.
I was told to double a SAN which means having two identical SANs with some sorts of replication to protect data in case a whole SAN failure.
In each SAN, I also have multipath IO, dual controller, dual switches...etc ?
Is it a overkill ?

Thanks for any idea out there.
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Question by:nothienthu
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by:tpitch-ssemc
ID: 38864008
Everything you listed I would call normal. I'd make sure you also have multiple arrays with hot spares at a minimum. Budget depending, I'd also get another SAN and replicate everything over for your DR plans. I will not run a SAN unless I have 2 controllers connected to different switches.

For example, I had an EMC VNX that had 2 controllers with 4 iSCSI NICs each. Of the 4 iSCSI NICs I would have 2 going to switch A and 2 going to Switch B then I would do the same thing for the other controller. That way if I lost a switch I would only lose 50% of our paths.

Of course 2 SANs are better than 1.
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millardjk earned 500 total points
ID: 38867714
Yes, whole array failures occur. It's typically unrelated to the hardware, but instead due to some unknown bug in the firmware that causes catastrophic data loss.
In those scenarios, they often trigger cascading data loss in replicated arrays (garbage in, garbage out), and the only thing saving the business using them is a good set of backups.

Those tend to be doomsday scenarios, however. You can read about them occurring, however, so it is something to assign a level of risk when designing your failure scenarios.

So yes, consider duplicate SANs as one mode of risk avoidance; having duplicate connectivity gear and multiple paths is another; multiple hosts running hypervisors and UPS backed by generator are yet others. It all comes down to how much cash you can afford to spend on them, and whether there is additional value (like providing more capacity or performance) beyond that of eliminating a single point of failure.
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