ISCSI multipathing issue

[azel]

Hello, i got a problem with my config of iscsi multipathing.

I got a DELL MD3200i connected to several servers (2 nics each) and i see my datastores.

But when it comes to load balancing, i can only ping or vmkping only one ISCSI nic on the san.

Here is a typical config :

on the 3200i

raid 0 NIC 1 : IP : 192.168.130.101     MASK 255.255.255.0

raid 1 NIC 1 : IP : 192.168.130.101     MASK 255.255.255.0

on the esx server

one vswitch dedicated to iscsi with 2 vmk

ISCSI1  IP 192.168.130.50               MASK 255.255.255.0

ISCSI2  IP 192.168.130.51               MASK 255.255.255.0

Of course on each VMK i got one active nic ans one unused.

They both are linked in the iscsi adapter and if i unplug one, the other will (eventually) see the SAN but i can't use both at the same time. For example, pinging the SAN interface will work with only one IP address (even though in the details of the ISCSI software adapter, the 4 ways are active and).

What did i do wrong (or forgot) ?

Thanx in advance

[vlho]

Hi Azel,

change IPs of iSCSI Targets and Initiators so that they will in different segmets

and do two vSwitches

See here for example:

http://en.community.dell.com/techcenter/virtualization/w/wiki/3043.aspx

[scottyyyc]

There is no need to segment the iSCSI network, unless you really want to.

I've run into this a few times with EqualLogics. The issue is the software iSCSI adaptor will only bind to one VMK port by default. It's easily fixed by running the following commands:

Example: Connecting Software iSCSI Initiator to Two VMkernel Ports

This example shows how to connect the software iSCSI initiator vmhba33 to VMkernel ports vmk1 and vmk2.

1 Connect vmhba33 to vmk1:

esxcli swiscsi nic add -n vmk1 -d vmhba33

2 Connect vmhba33 to vmk2:

esxcli swiscsi nic add -n vmk2 -d vmhba33

3 Verify vmhba33 configuration:

esxcli swiscsi nic list -d vmhba33

Both vmk1 and vmk2 should be listed.

In this example, if you use the vSphere client

[rickardnobel]

In vSphere 5 there is also a graphical interface for binding the Vmkernel - iSCSI adapters.

[azel]

Hi, i got vsphere5 and both VMK are binded to the software adapter.

But only the ways one one NIC are tagged "active (I/O)" the other ones are only tagged "active"

is there a problem with the graphical interface in vspehre 5 or (most likely) did i miss something ?

[azel]

By putting the 2 nics and the 2 vmk in different subnets, i managed to be able to ping and vmkping both nics on the san.

BUT (there's always a but ...) in my software adapter configuration, 1 only got half the ways active (vsphere only communicates with one NIC)

is there a special configuration on the 3200i to specify i want an active/active communication ? (i've already put my datastores in round robin mode)

thanx in advance

[rickardnobel]

Do you use the 192.168.130 network just for iSCSI or is there any other use? (Managment, vMotion or similar.)

[azel]

just for ISCSI.

[Fatalglitch]

iSCSI on VMware does not route, so you need to be careful what subnets you put your vmk's in

[Fatalglitch]

The Dell 3200i does not support RR to the same LUN over multiple interfaces. I'll dig up the reference, but I've seen the issue before, and that was the conclusion each time.

[Fatalglitch]

On an MD32xxi, each disk group is owned by a controller and the LUNs are assigned out of those disk

groups.  Only one controller at a time has access to the LUNs.  The alternate controller has access to

those LUNs but only as a failover alternate path.   This LUN/controller relationship is reported by the

MD32xxi to VMware which then dictates the paths (and the "optimal" condition of the MD32xxi).  

Page 53

http://www.dell.com/downloads/global/products/pvaul/en/md-family-deployment-guide.pdf

[azel]

So i cannot use multipathing with a 3200i ? just failover ?

[Fatalglitch]

You can multipath amongst the controller, but not across controllers. You will still be bandwidth limited by how many ports are available on the Active controller.

[azel]

But if I connect more than 1 NIC on the same controller, the second NIC is marked as "not used".

How to force the use of the 2 nics ?

I'm starting to wonder if it's even possible to multipath on a 3200i

[Fatalglitch]

Again, from the same document I linked above:

"Nothing requires you to use all four ports for a given server but if you are going to use Round

Robin (RR) then using all four ports is recommended. If you choose to use all four ports then they need

to be on separate subnets and if you need to use vLans you’ll need separate vLans for RR to work

correctly"

See page 10.

I recommend you read very closely through that document, as it is still very valid in vSphere 5. Every storage array acts differently, so you need to fully understand yours in order to get it running correctly.

[azel]

With all the documentation provided and your help, i managed to configure an effective multipath with 4 nics (2 active and 2 failover) for each of my servers.

Thank you