MD3000 - Too many paths?

[L0cayta]

Hi there.

I currently have a cluster of esxi 5.0 hosts hooked up to some iSCSI SAN storage. I'm using a Dell Euallogic PS6100XS which works fine as my primary storage.

I have just hooked up an older MD3000i to my hosts and placed it on my iSCSI network. The MD had one controller which two NIC's and will be used as a backup / DR device.

Attaching the storage i've created to my cluster there appears to be an unusual amount of paths listed for my MD's volumes.

Each ESXi 5.0 host has a vswitch configured for iscsi trafficwith two nic's assigned for MPIO. WOrks fine on my Equalogic wherer each volume has two active i/o paths

My MD volumes for some reason show 4 active i.o paths. Has anyone seen this before as i can't work out how these voluems would have 4 active paths for a volume?

[mcowger]

Seems right to me, assuming your storage network is fully meshed.

2 nics per host * 2 nics per controller * 1 controller = 4 paths.  Because all paths go to 1 controller, they should all be active.

[L0cayta]

The paths appear differently from my MD to my Eqlallogic.

A volume mounted within my ESXi host from my Equallogic has two paths. The Equallogic has 4 NIC's on it's active controller.

A volume mounted within my ESXI host from my MD3000i has 4 paths. THe MD has 2 NIC's on it's single controller.

[mcowger]

EQL is not a good comparison point here - they play a lot of strange games with iSCSI target redirection, etc that are somewhat uncommon.

[L0cayta]

Looking at my EQL connection, ESXi has two paths 'Active I/O' to 2 different NIC's on the SAN which have static IP's assigned.

The MD connection has the 4 'Active I/O' paths, x 2 paths per NIC on the MD which also have static IP.

Taking the EQL out of the equation as it handles iSCSI traffic in it's own way would you say that my MD connection looks right?

[mcowger]

Thats what I'm saying - the MD count seems right to me.

[Vannus]

The EQL SAN will use a 'Group' address which manages access to the controller interfaces, so you should see 1 path for each iSCSI interface on your host, the EQL controller will do all the load balancing for you at the controller end. (you should only need the group address as your iSCSI target)

with the MD there is no concept of a group address, so each interface on your host can potentially see ALL interfaces on the MD controller (the extra paths you see in your case). You should be setting up each controller interface as an iSCSI target.

The recommendation form the MD setup guide is to place each port on the MD controller in its own VLAN and have one interface per VLAN on your host. all load balancing is then handled buy the ESXi multipathing (assuming youse set up multipathing correctly on the host). This will prevent unnessesary paths being seen and reduce your rescan times.