I strongly recommend one path to each node, with a 1:2 fan out ratio.
Host port 1 to SANSWITCH-A to Node0,Node1 Host port 2 to SANSWITCH-B to Node2,Node3
When I create the aliases for a new inserv, I will divvy them up into "sets" and rotate hosts around the sets to keep all the front end ports balanced easier. example:
Node0, port1 - switch A Alias: V400_0-3-1_SET1 Node0, port2 - Switch B Alias: V400_0-3-2_SET2 Node0, port3 - switch A Alias: V400_0-3-3_SET3 Node0, port4 - Switch B Alias: V400_0-3-4_SET4
Node1, port1 - switch A Alias: V400_1-3-1_SET2 Node1, port2 - Switch B Alias: V400_1-3-2_SET1 Node1, port3 - switch A Alias: V400_1-3-3_SET4 Node1, port4 - Switch B Alias: V400_1-3-4_SET3
Node2, port1 - switch A Alias: V400_2-3-1_SET3 Node2, port2 - Switch B Alias: V400_2-3-2_SET4 Node2, port3 - switch A Alias: V400_2-3-3_SET1 Node2, port4 - Switch B Alias: V400_2-3-4_SET2
Node3, port1 - switch A Alias: V400_3-3-1_SET4 Node3, port2 - Switch B Alias: V400_3-3-2_SET3 Node3, port3 - switch A Alias: V400_3-3-3_SET2 Node3, port4 - Switch B Alias: V400_3-3-4_SET1
So Host1 would get zoned to SET1, Host2 to SET2, and so on.
The benefit of this is you can have a SAN-A or B network go down, and your hosts will still be making balanced use of all 4 nodes. If a node goes offline for maintenance or unplanned outage, its a 25% hit to all your hosts, and not a 50% hit to some. Assuming you're using 8 gbit ports on the storage, and 8 gbit ports on the host... this waters down the impact a single host can have on your system's front end ports... if you use a 1:1 zoning of host port to Inserve port, then a poorly written app could blast 8 gbits of data and saturate a storage port also running at 8 gbit, thus causing high wait times for other hosts that share those ports. If you use the 1:2 zoning, your 8 gbit of host HBA gets round robin'ed to split to multiple 8 gbit inserve storage hbas.... thus that monster query that puts the host HBAs at 100% will only bring the storage ports in the set to 50%, leaving breathing room for other systems that share those ports.
_________________ Richard Siemers The views and opinions expressed are my own and do not necessarily reflect those of my employer.
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