iSCSI NICS. Help please

Question

I was wondering how microsoft solve the isue for the iSCSI NICs. I have read many articles of take two or four dedicated NICs for iSCI. How can you use it when teaming is not supported? Yes I know the article http://support.microsoft.com/default.aspx/kb/968703

We have one Netapp (2040) with two teamed nics in it, they are going too two HP 3500 switches that use distributed trunking (so 1 IP is distributed). So the servers have to dedicated NICs in the same subnet. When you run the cluster validation, he gives a warning that multiple nics are in the same subnet. Can I safly ignore the warning?

If you create a new vhd file on a node that is not the cluster owner, I see that the management NICs are fully (50%) loaded but the iSCSI NICs are doing nothing. When you look on the cluster owner, you see the management and the iSCSI NICS are loaded for 50% is this a normal behavior? We use CSV, why does it not write directly to the CSV lun?

Regards, Tore Trygg

Answer 1

Since you have mulitiple issues in your posting, I will attempt to answer each one separately in turn.

First, if the NICs are properly teamed, they will appear as one NIC in the cluster validation. If not, make sure that you have NIC drivers that support teaming. Setting two NICs to different addresses on the same subnet is not sufficient.

For iSCSI, it is actually preferred that you use multipath I/O (MPIO) instead of teaming for your connections to the SAN fabric. The SAN manufacurer (in your case, NetApp) should have provided you with a device-specific module (DSM) for MPIO that must be installed on every client that will use multipathing to the SANs. If you end up using an MPIO DSM, you will still get the cluster validation warning about two NICs on the same subnet, but this can then be safely disregarded. Multipath setup can be tricky, so be sure to follow your vendor's installation instructions closely.

For cluster operations (once the cluster is created), you can configure which network connections the cluster should use for communications. As a best practice, it is recommended that your SAN fabric should be used only for SAN communications. Therefore, those NICs should not be selected for cluster communication. If you are in a situation where you only have two NICs, you're probably better off just using one connection for the SAN and the other for all other traffic. Additionally, be sure to use dedicated switching equipment (or at the very least, a separate VLAN on the switch) for your SAN network. Network contention can severely impact SAN performance.