Cisco UCS Appliance Ports for NFS Storage
Although not new to 2.0, the Appliance Port has been one of those rarely seen Unicorn type use cases out in the field. That being said, I think it’s a solid way to connect storage via NFS directly to the Cisco UCS domain, since (with pretty much any IP based storage) we don’t want to be routing the packets anyway. In a vSphere deployment, this would create a nice, tightly wrapped environment that doesn’t rely on higher level switching.
There are a few caveats, mainly for failure situations, that require consideration. While this post is intended as a guideline on the “how do I do this”, be aware of the “should I do this” thoughts. NetApp has written an awesome whitepaper entitled “Cisco Unified Computing System (UCS) Storage Connectivity Options and Best Practices with NetApp Storage” that has an entire section devoted to failure scenarios with Appliance Ports – it’s a very interesting read! Also, I’ll pay homage to some other blog posts that I read on the subject.
Some goofy stuff can happen in a failure scenario!
Without further ado, here are some steps to get Appliance Ports working for you.
The Desired Layout
In this case, I’m using Appliance Ports to connect to a storage appliance that has a pair of storage processors, A and B. The storage will be linked directly to the fabric via 10GbE cables on port 1/30 and 1/32 on both interconnects.
This is a pretty standard wiring configuration that eliminates single points of failure.
First, the ports on the Fabric Interconnects need to be assigned as Appliance Ports. Select the ports that need to be assigned, right click on one of them, and choose “Configure as Appliance Port”. I’m using port 30 and 32 on a 6248UP (last two bottom ports on the right).
Unlike a Server Port, which just says “OK I’m done”, the Appliance Port requires some configuration. Realistically, all you need to do is assign some VLANs … oh wait, there are no VLANs! What gives?
Appliance Ports use their own special Appliances VLAN Cloud, which is separate from your normal LAN Cloud. You can either make them on the fly while configuring the ports, or prepare them ahead of time. For this particular scenario, I’ll just go ahead and generate one on the fly: VLAN 254, which I use for NFS traffic. Note that I select “Common/Global” so that both Fabric Interconnects use the VLAN.
Now that a VLAN is available, I’ll select it to enable the VLAN and mark it as a native VLAN so that my storage appliance does not have to tag packets. I tend to also select the default VLAN (1), but this is optional.
There’s also an option at the bottom to enter a MAC address for the “Ethernet Target Endpoint”. If the storage appliance does not advertise its MAC address, you’ll need to enter it in manually here. Because the UCS domain is limited to layer 2, a valid MAC address is required by some means in order for the mac-address table to populate. Fortunately, most all storage appliances (or at least the good ones) should not require using this feature.
Repeat the process for the other Fabric Interconnect.
Once completed, make sure the storage appliance has an IP and is operational. You should be able to ping the interface from within the UCS environment (such as a blade or a fabric interconnect).
If there is a connectivity issue, ensure that the mac address-table has updated with the storage appliance’s MAC address. Connect to the fabric via SSH and issue the command:
connect nxos show mac address-table
You should be able to find the MAC address of the storage appliance listed. If not, try using the Ethernet Target Endpoint or verify your layer 1 connections.
If you want to make changes to the configuration, you’ll have to edit the ports directly. You can’t just make adjustments to the Appliances Cloud and expect anything to change.
For example, let’s say I needed to add VLAN 255 to the Appliances Cloud, and then set it as the native VLAN. I have made the changes in the Appliances Cloud as shown here:
But the ports do not reflect the change.
Bottom line – if you need to make a change to the Appliance Ports, you’ll have to visit the ports themselves and edit the VLANs using the “Configure VLAN” link.
Appliance Ports are a nifty way to staple storage directly to your Fabric Interconnects at layer 2, which keeps traffic off your higher level aggregation or core layer switches. It also helps eliminate a lot of latency and wire time, too. However, be aware that there are a lot of considerations to be made when failure strikes. Unless the storage is also aware of the failure and shifts traffic to an interface on the surviving path, you may result in an environment that is degraded or in a full outage.