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Multipath to LUNs

i know the Vseries only have two paths to a LUN. question is, how can i have more than 2 paths to a LUN. my backend array is a 3PAR which has 4 controllers. the 3par can still operate if 3 controllers go down. Currently, the vseries only attached to 2 controllers; if at any point, both controllers go down, my system is SOL because the other two controllers are not attached to the vseries.

any idea or recommendation to have the vseries see all four controllers so a panic will not happen if two controllers or more controllers go down?

thanks

Re: Multipath to LUNs

Hi Joey,

Data ONTAP 8.1 running in Cluster Mode is able to use 4 paths to a given array LUN.  Otherwise, what you are asking for is protection against two points of failure, something few systems are designed for.  In the failure case you mention, your data would be OK.  It would suffer a loss of availability, but you could zone in the other operational array controllers to regain access.  If you need protection against more than a single point of failure, Cluster Mode is your only solution.  However, I don't think it's likely you would lose more than one controller.

Thanks!

- Dan Isaacs - NetApp

Re: Multipath to LUNs

daniel

thanks for sharing your input. question, since this is currently POC, can i install clustermode and try out CM and if i dont feel its what i need then reinstall 7mode again?

thanks

Re: Multipath to LUNs

If availability is primary consideration, it is possible to make one set of LUN available via one pair of controllers, another set of LUNs – via another controller pair and SyncMirror between them.

Re: Multipath to LUNs

Joey,

Cluster Mode would require additional hardware, and the arrays may not be supported. Cluster Mode array support won't be complete until DataONTAP 8.2.  Switching modes is not yet a user-supported process, and may introduce undesirable complications for a POC. If you have no previous experience with it, I would not recommend using it in a POC.  

If there is a NetApp SE or partner manager that you usually work with, you can reach out to them for more detailed examination of the benefits of 7-mode vs. Cluster Mode.  FWIW, we have hundreds of V-Series deployed with 3Par, and this has never been an issue. 

Thanks!