Blog Posts

I've been a user of Fibre Channel SANs for about eight years. I have used the Dell | EMC-based arrays throughout and have gone through a few product transitions from the FC4700 to the CX-600 to most recently a CX3-80. I always liked the Navisphere management tool and was able to great performance across the range of applications that I set up to use the Fibre Channel storage.

About eight months ago I was finally convinced to try out some iSCSI arrays. First, I worked with the Dell | EMC CX3-40c, which has both iSCSI and Fibre Channel ports. This configuration didn't really seem all that different from what I was used to with Fibre Channel, mostly because I was still using Navisphere. Next, I set up and used a PowerVault MD3000i and found this array to be really easier in some ways, although it didn't have the same features in lots of respects. Finally, about four months ago I started using some Dell EqualLogic PS5000 Series iSCSI storage arrays. And I did some performance testing with them in a whitepaper that was released about a month ago. The net was that this setup is really much easier, and I was able to get great performance.

We are having a chat here on delltechcenter to discuss when to use what type of storage for virtualization, and we expect a lot of the discussion to be about iSCSI versus Fibre Channel. Feel free to join the chat or check out the transcript, depending on when you are reading this.

I haven't done a head-to-head performance comparison of Fibre Channel versus iSCSI, and I don't plan to either. I've been able to get great performance with both in the tests that I have run. It's more the ease of setup and use that makes iSCSI so compelling for me. I had resisted iSCSI for a while because I just knew that it wouldn't be good enough, but now that I have started using it I find that it works fine. I think that Fibre Channel still has places where it fits best, but I would highly recommend that iSCSI be considered for all new projects. I'm still using both in my lab. You just might find that you will like iSCSI-if you try it.

Todd

To follow up on the Hyper-V Server install video from last week, I added a new page to delltechcenter.com that shows how to configure a connection to an iSCSI storage array for Hyper-V Server. With a full Windows Server 2008 installation there is a GUI tool in Administrative Tools called iSCSI Initiator that is used to configure and manage these connections. Windows Server 2008 Core and Hyper-V Server do not have a GUI, so a command-line version called iscsicli.exe must be used.

The page that I added shows how to create a simple iSCSI connection by first enabling the iSCSI Initiator service with the sc (service console) command, then using iscsicli.exe to map the connection to the target iSCSI LUN, and then using diskpart.exe to do the partitioning and formatting. It's not as bad as it sounds, and is pretty straightforward once you know the commands.

To get an MPIO-type connection set up is only a little bit more involved. There is a script that I found in a Microsoft TechNet forum that is an example of how to do an MPIO connection to an MD3000i using iscsicli.exe. You can also use a GUI-based tool called Storage Explorer that is included with Windows Server 2008 to connect remotely to the Hyper-V server and create additional connections. (It doesn't see anything until you have used iscsicli.exe to get the initial connection.)

Todd

In response to a few questions that came up, I put together a video that shows how to do a cool trick with Microsoft Excel to create graphs of MD3000i array level performance data. I posted an entry here last week and also put up a wiki page about how you can use the smCLI command line tool to get array level performance data (Individual storage processors, array totals, and individual virtual disks) from an MD3000i. The output of this command is a csv (comma separated values) text file. I included on the wiki page a nice graph of the performance based on the data from this output file. What I didn't go into was how to create such a graph.

So now you have this great little video that will show you one way that you can use Excel to create a graph based on the data in the file. I don't claim to be a know-it-all when it comes to Excel, but the way that I do it in the video works. I would love to hear from anybody who knows of other (possibly better) ways to do it.

Todd