Clariion active passive architecture

One starting point would be the EMC document "EMC Unified Storage Systems Fundamentals for Performance and availability".  This briefly discusses Active/Passive and ALUA.

As far as 4 SP port zoning, this is common availability.  Typically, you zone each initiators in a manner as follows:

Host HBA port 1 - SPA port 2

Host HBA port 1 - SPB port 2

Host HBA port 2 - SPA port 3

Host HBA port 2 - SPB port 3

Why?  In the above scenario, we protect against the failure of an SP port or a full SP failure.  If we lost port 2 on either SP above, we can still communicate on the same Host HBA and we have no trespassing required on the array.  If we lost SPA or SPB, we would trespass LUNs from one SP to the other and still be able to communicate on both host HBA ports.

If we only zone to one port on SPA and one port on SPB, if we trepassed LUNs, one HBA port will immediately be degraded and communicate with the array on a non-optimal path (i.e., it would send traffic to the failed SP port which would communicate on the internal path between the SPs). 

Let us know if that helps!

Karl

You can also read the whitepaper "EMC CLARiiON Asymmetric Active/Active Feature" as well:

http://www.emc.com/collateral/hardware/white-papers/h2890-emc-clariion-asymm-active-wp.pdf

Active/passive means only one storage processor processes I/O to its owning LUN. The other storage processor would never process i/o to the non-owning LUN.

zeroing 4 paths has several benefits.

1. To tolerating i/o module failure and SP failure respective. In some cases, all the paths to say SPA is the optimal path and you would prefer i/o always go this way. If one of the i/o port failure on SPA, it would be better we can still handle i/o on SPA through another i/o port rather than trespass the LUN to another SP.

2. LUN trespass would cause a little bit long delay and might interrupt the application.

3. peer SP would become unbalanced after the reassigning of the LUN ownership.