connect iSCSI SAN to 2 hosts

[Fred1234]

Are there instructions for the best practices for connecting an iSCSI SAN to two ESX 4.1 hosts?

If I make a vmkernel on our main virtual switch in the VLAN that the SAN is on, the ESX host can see the SAN in the Storage Adapters section, but I made a new separate virtual switch to put it on (as I read somewhere that I was supposed to do it that way) and now the host won't see the SAN.

What exactly is the correct way to configure this?  I need both hosts to access the SAN so I can vMotion the VMs back and forth between the hosts.

Fred

[DarkPassenger]

So it worked as you had the vmk on your main vswitch but not on an dedicated vswitch? That sounds strange. Did you doublecheck the portgroup settings? Did you run a rescan?

[Fred1234]

I did run a rescan, and it doesn't show up.  I don't know what the port group settings are supposed to be, or where to check them.

Regarding making it work on both hosts, am I supposed to just make an identical vSwitch and vmkernel on the other host?

[Fred1234]

Here's how I have it working right now:

I made an identical vmkernel (in the same VLAN that the SAN is in) on both hosts on our main vSwitch, except I gave a different IP to each vmkernel.

In Storage Adapters, for the iSCSI adapter, I entered the iSCSI name and all the other settings the same on both hosts, and the SAN showed up.

I've made a VMFS data store, and put a VM on it.  I tested vMotioning the VM between the two hosts without issue, so it seems to be working.

Is there anything wrong with the way I have it set up?  Is there a reason I should have the iSCSI vmkernel on a separate vSwitch?  The vSwitch I have it on is used for everything, but it uses 5 physical NICs, so bandwidth shouldn't be an issue.  Is there a PDF or something with the best practices for this setup somewhere?

Fred

[DarkPassenger]

So it is working right now?! I think I got that wrong. It is best  practice to have a dedicated vSwitch for your iscsi vmk portgroup for  several reasons. There is no "real" load balancing among the vmnics on a  vSwitch, as long you don't configure each portgroup to use other vmnics  than the other pgs.

It's also considered to be more secure although I couldn't point out a special scenario where this counts right now.

There is a storage best practice guide which you can download on vmware.com.

EDIT

I can't think of any reasons why it should't work on a dedicated vSwitch while it's working on your main-vSwitch. Just Check that the vmk iscsi portgroup has the same IP like before on the main-vSwitch and the VLAN is set correctly. Of course you have to remove the old one.

[Fred1234]

I got it working right before I typed that last message.  I'll look for that storage best practices guide.  Thanks for your help.

[Fred1234]

Update: With the way I had it set up, I was getting an alarm every few hours that one of the hosts lost connectivity to the SAN.  It would regain connectivity after a few seconds.  Sometimes it was one host, sometimes the other, but not both at the same time.

So I tried again to set up a VMKernel on a separate vSwitch, and I figured out why it wouldn't work before: I tried not specifying a VLAN in ESX, since the physical NIC was plugged into a port on the physical switch that was already set to be on the VLAN that the SAN is on.  It works that way and sees the SAN, but still loses connectivity like before.

I found and looked through VMware's "iSCSI SAN Configuration Guide", but didn't find anything about setting it up for multiple hosts.  Am I supposed to make another iSCSI Initiator on the SAN for the second host to connect to?  I have them both connected to the same one with all the same settings, including the same IQN.  Is that how it is supposed to be?

[Fred1234]

Attached is a pic of how the vswitch looks on each of the hosts.  If I have the SAN connected to only one host, it doesn't lose connectivity.  I tried having a service console on the vswitch on each host, and it still had the issue.  I've also installed all of the latest updates to ESX 4.1.

[AndreTheGiant]

There are different iSCSI SAN topologies depending by the storage type.

Usually you have to check storage vendor recomandations.