NOS 2.1.x - The VTIP is dead, long live the Discovery Address!

In Nimble OS (NOS) version 2.0.x we introduced the concept of a Virtual Target IP address (VTIP). As shown below, this was in addition to the Discovery IP address (which was limited to a single Data subnet) and was used to make dynamic iSCSI connections possible. Hosts could connect to a Virtual Target IP (VTIP) address, and then the resulting connection was automatically redirected to an appropriate data IP address. The VTIP address could be moved across network interfaces. There was no I/O traffic on a VTIP. You can see what this looked like in the NOS 2.0.7 Network Administration settings:

In NOS 2.1.x we have retired the “VTIP” and instead have allowed the use of multiple discovery Addresses, one per subnet, in effect combining the VTIP and Discovery Addresses to achieve the same task.

Now, each subnet can have its own Discovery IP address. This enables the iSCSI initiator to discover iSCSI targets for the volumes on the array.

This IP address can be used for data as well as management in a single shared network.


Discovery IP Addressing Explained:

Discovery IP addresses make dynamic iSCSI connections possible. When a dynamic iSCSI host connection is enabled, the Nimble storage group exports a Discovery IP address. The host connects to the Discovery IP address. Then the resulting connection is automatically redirected to an appropriate iSCSI data IP. This is also called a dynamic connection. When a dynamic connection is broken, a new connection to the Discovery IP is automatically created and then rerouted an iSCSI data IP as a new iSCSI session.

You can enable dynamic iSCSI connections when you choose the Automatic iSCSI Host Connection method.

When you choose the Manual iSCSI Host Connection method, you have a static iSCSI connection. In that case, the Nimble storage group exports the data IPs as target addresses. When a static connection breaks, a new connection to support the same iSCSI session is automatically created.

Note: Discovery IP addresses and dynamic iSCSI host connection are required when there are multiple Nimble arrays in a storage group.

There is no I/O traffic on a Discovery IP. But a Discovery IP address can be moved across network interfaces, the eth ports on the back of the Nimble array.

These are shown in the subnets tab of the Network Configuration screen below:

The next few screens show the various tabs available in the 2.1.x interface starting with the Group tab:

Clicking on the subnets tab, allows us to view/edit the subnet settings:

Clicking the Interfaces tab allows us to view/edit the individual Interface ports:

Clicking on the Diagnostics tab, allows us to view/edit the Diagnostic address settings:

So let's make some changes.

From the subnets tab, we can edit the subnet settings by selecting one subnet at a time, in this case for the subnet (Management):

This is where we set the Discovery IP Address for each subnet:

We don't actually need a Discvery Address in the Management network, this is optional and could be removed as we can have a subnet specific Discovery Address wthin each defined subnet.

Here we select the subnet for the subnet (in this case the Data subnet):

We are able to edit the Discovery Address as required:

If we have multiple Data subnets defined, e.g. to segregate our Data subnets, we are able to set a Discovery Address per subnet/VLAN.

Note: the other network settings mentioned here (multiple subnets/VLAN Tagging) are described in other blogs in this series.