iSCSI Multipath esxi hypervisor 2nics to Dell Ps4100 2nics - How many paths?

[BKFrancescoB]

Hi at all.

I am trying to configure a multipath for the iSCSI connection that I have made between an esxi hypervisor 5 and a storage DELL PS 4100. This ISCSI traffic goes through a dedicated VLAN, numbered 110. I have the storage in one rack, the esxi hypervisor in a second rack. Racks are connected with optical fiber through ISL. Switches used for this implementation: 4.

DELL PS 4100:

1 controller with 2 nics (eth0 eth1). Each connected to two different switches of rack B. Between these switches I have an ISL (Inter Switch Link). eth 0 has its own ip, the same for eth 1. DELL uses a Group IP that groups logically eth 0 and eth 1.

ESXi Hypervisor is connected to switches of the other rack in an identical manner. Even these two switches have an ISL between them. 2 vmkernel port group in the same vSwitch tha has two uplinks connected to it. Each port group uses actively a vmnic different from the other one. The other vmnic, the one not used, is set Unused adapater in the port group properties. I have done the port binding vmnic - vmknic in the iSCSI software adapter for both vmnics.

Now, how many paths I would have to expect to see when I put in the dynamic doscover the Goup IP address of the storage?

Thank you very much.

Francesco B.

[BKFrancescoB]

Can you reply to my question please?

Thank you

[thibaudpeter]

Hi,

I recon you shoud expect 4 paths per LUN
ESXIP1  -> PSIP1 -> LUNx

ESXIP2  -> PSIP1 -> LUNx

ESXIP1  -> PSIP2 -> LUNx

ESXIP2  -> PSIP2 -> LUNx

Does that suit you as an explanation ?

Path Selection Policy with ALUA

[Nick_Andreev]

Hi Francesco,

If you have two ports configured on a ESXi server and two ports configured on the EqualLogic array and all ports are on the same network subnet, then you should see four paths between each ESXi server and the array/LUN.

If you had two controllers in the array, then you would see 8 paths between a host and the array, but only four paths to each LUN. Because majority of storage arrays does not support ALUA for iSCSI and can present iSCSI LUN through one controller only.

Another scenario is two iSCSI subnets, where for two ESXi ports and two array ports you get two paths, because of the traffic segmentation between two subnets.

Hope that helps.