Published: December 1, 2011
No, I didn't do a typo and mean to say "Every Windows Server has an iSCSI Initiator."
And it may only be a slight exaggeration when I say "Every."
But did you know that your Windows Server 2008 R2 server can also be an iSCSI Target? I didn't.
Typically, one thinks of an iSCSI Target as a SAN appliance offering block storage (not files) over commodity Ethernet, instead of Fibre Channel. Then, your production machines use their iSCSI Initiators to connect to it. And voila, a new disk magically appears in your Windows disk administrator view and your Ethernet activity light will likely go crazy from then on; separate network segment and NICs are highly recommended. (slightly oversimplified)
Starting with Windows Server 2003 and Windows XP, Microsoft has provided an iSCSI Initiator, for production machines to utilize iSCSI block storage -- but with the assumption that those blocks were coming from an iSCSI storage appliance or Storage Server (read on).
For years, Microsoft shipped a special edition of Windows Server through OEM partners like Dell and HP. The OEMs would then take the base server hardware that they shipped and tune it and pre-package it with "Windows Storage Server," which was essentially Windows Server with some tuning for file/storage IO, as well as some differentiating technologies that had not yet been included in the mainline of Windows -- particularly technologies that were suited towards appliances. One of those technologies has been an iSCSI Target, so that the Windows Storage Server could be both a file-sharing and block-sharing appliance.
Disclosure: I was Microsoft's product manager for Windows Storage Server 2008, along with some time with WSS 2003 R2 and leading up to WSS 08 R2. Check out my blog archive for all of my WSS posts: http://centralizedbackup.com/index.php/tag/windows-storage-server, including:
In some ways, WSS was an incubation platform for trying new storage technologies before they might later merge into mainstream Windows Server. The iSCSI Target software was one of the last unique WSS technologies that hadn't yet made it into WS ... until now.
Last month, I was visiting several product teams in Redmond when one of them mentioned that their iSCSI Target is now available to everyone. What?!?! I hadn't heard that, did you?
Yep, sure enough - as of October 2011, you can now download an iSCSI Software Target for your Windows Server 2008 R2 platform.
I am a hands-on guy, so as soon as I got back to my office, I tried it and it works! Essentially, you create LUNs by creating VHDs and then share them as block storage via iSCSI with production clients.
Is a VHD built on top of the Windows File System as fast as native storage? Actually, it's pretty close. It didn't used to be. If you look at the benchmarking and best practice guides put out by the Hyper-V team, they aren't adamant in saying to use "raw" disk anymore - they say that VHD performance is now equitable. So, at least accessing the VHD blocks are about the same as accessing the file system of that Windows Server. Your network to the server and its underlying storage performance still need to be engineered correctly.
How does it compare with iSCSI appliances, especially those offering CIFS shares for unified storage? Well, in the past, some customers have moved towards appliances that were offering blocks, and began offering file shares too. Arguably, this levels the playing field a bit, since your Windows Server, which already offered files, can now offer blocks. OK, maybe not a level playing field, but it changes the conversation.
How is the performance? In my small branch office, it was good. It was relatively easy to set up and I've seen no real lag on my machines compared with their local disks versus their iSCSI-mounted storage. Am hoping to eventually do a true ESG Lab validation to put some load on it and really dig in.
We all know that most server hardware has untapped performance today. Usually, it is an argument for virtualization and consolidation. But what if we were to add non-traditional functions to our server, like block storage? That proposition gets even more interesting if the claims of Windows Server "8" come true.
Do I expect to see iSCSI from Microsoft displace storage appliances within the data center? Not yet. There is still huge functionality that appliances offer over just giving blocks (thin provisioning, deduplication, tiering, etc.), where simply serving up the blocks is table stakes. But by that definition, Microsoft and its millions of Windows Servers can now claim to have those table stakes. As to the advanced functionality of a real storage appliance, ask me again after WS"8" has shipped and we see where its R2 is headed. But in branch offices where you likely already have a Windows Server and may never be able to justify a standalone appliance that offers those storage capabilities, why wouldn't you download it and see if it met your needs?
Of course, you would have to know that it was available, which I and likely many others didn't -- but now you do.
Thanks for reading,
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