One requirement or recommendation when creating a SAN that utilizes iSCSI is to separate the physical MPIO segment to permit full bandwidth utilization for the Initiators. This would also allow the network to operate with Jumbo Frames and minimize any potential conflicts with machines or adapter that may not support that capability and force the sessions to fall back to a lower MTU value. It also lessens the likely hood that an unmanaged switch will become a problem as it only needs to deal with a one frame size. This is probably not much an issue, and with more expensive switches it obviously isn’t; however, I’m using consumer grade dumb switches that only cost me about $30 USD.
The problem that you will run into with the Western Digital business line of storage servers is that they only provide two integrated Ethernet ports. So you either have to cripple the MPIO by using one port for iSCSI on a separate segment, or put both ports onto the LAN segment (not a good idea).
I stumbled upon a simple solution to this, add a USB 3.0 adapter to the unit and put both ports into the separate segment. The device I used was originally purchased for my Surface Pro 3.0, but it works and actually supports Jumbo Frames. The device can be found on the Microsoft Store here.
Figure 1: Separate the MPIO network
I would say that if I really wanted to provide some fault tolerance, I could add another dumb switch and segment the MPIO further, but in my test cases that design has worked great. I’m currently hosting 4 virtual machines over iSCSI via the target sever (DX4000) to a Hyper-V Server running on the HP ProLiant G7 Micro server.
Here’s a snap shot of one of the performance tests I ran using ATTO Benchmark over MPIO between the G7 and DX4000. The first image is from the DX4000 showing utilization of both Ethernet ports dedicated to MPIO and provisioning a single VHD to the Hyper-V host. As you may notice, the last two Ethernet ports reached up to ~708Mbps each for a total bandwidth of around 1.4Gbps. Not too shabby.
Figure 2: MPIO Provisioned over Gigabit
Here is a snap shot from the Hyper-V host on the G7 during this ATTO Benchmark test. The maximum throughput reached a speed of about 160MB/sec, fair for an inexpensive SOHO MPIO solution.
Figure 3: G7 ATTO Benchmark to VHD over MPIO
This would probably create some scowling views from most data center managers; however, I found this USB 3.0 adapter to be a slick and reliable way to get an actual management network running to do general RDP or other tasks. Recommended? Probably not, but it works… so why not.