We've seen an uptick in "direct attach" storage deployments on the Cisco UCS 2.0 platform lately-- and there doesn't' seem to be a lot of good information available for this type of deployment. It's not hard to make work-- in fact, rather simple-- but once you go down to the hypervisor level, there seems to be much confusion and little detail available from Cisco or otherwise.

First, it's important to understand what "direct attach storage" means in the Cisco UCS context. If you were to take your storage array (only a handful of them are certified by Cisco for this deployment mind you) and connect it directly in to the Cisco UCS Fabric Interconnects, it would be considered a "direct attach" deployment. This type of connectivity uses "Appliance" ports, which you simply configure though the UCS Manager by select the desired interface, and "Configure as Appliance port".

With this configuration, you must create the necessary VLAN under the "LAN" tab within the UCSM below BOTH the "Appliance" VLAN section, and the "LAN" VLAN section. This is required-- as all "Appliance" ports pin to a traditional "uplink" port, and if the VLAN does not exist on the uplink, the Appliance port will not come up. This is what provides the capability for communication to other storage ports in a "non-optimal" flow of traffic (see image below).

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To help minimize the amount of traffic that flows up the uplinks and "over" to the other Fabric Interconnect to access storage ports, we decided to use separate VLANs/subnets from within vSphere, and made sure our NICs were configured on the appropriate Fabric Interconnect. For those who are not familiar, when you create your virtual NICs for your service profiles, you select which Fabric Interconnect you'd like for them to be associated with. You also choose if you want to enable Fabric Failover (a feature I blogged about a ways back). In our case, we created vNIC 1 on Fabric Interconnect A. Then we used Subnet A with that specific vNIC to access the storage processor ports, also o