John Joyner explains how a free software package can transform Windows Server 2008 R2 into an iSCSI SAN provider and provide a cheap entry to private clouds with repurposed physical servers.
A new option for server storage entered the market April 4, 2011 when Microsoft made available for free public download a software package that transforms a standard Windows Server 2008 R2 computer into a Windows Storage Server, aka an iSCSI SAN provider. If you own, or purchase, a Windows Server 2008 R2 license, installing this small application turns your computer into a storage area network (SAN) appliance.
How it works (high-level)
Any physical server capable of running the 64-bit Windows 2008 R2 operating system, with at least two network cards, and lots of local storage is a candidate SAN device. Application servers (that will use the shared storage) also need one or more network cards reserved for iSCSI. After installing the Windows Server 2008 R2 operating system on your storage server, install the iSCSI Target software.
On the client computer that will use the shared storage, you enable the iSCSI Initiator, a built-in part of Windows Server 2008, or install the downloadable iSCSI Initiator software on previous Windows versions. Create shared volumes or VHDs on the storage server and present them to the application servers. On the application servers, such as Hyper-V hosts, you configure the iSCSI Initiator with the IP address of the storage server, and after a few clicks you see the disks in Disk Administrator, ready to initialize and format.In the case of Hyper-V virtual machines (VMs), the VHDs are presented as iSCSI targets to the Hyper-V host servers, one iSCSI target per VHD. See in Figure A how a VHD is stored on the storage server's local D: drive array, and shared as an iSCSI target.
Figure A - Create VHDs on a large volume on the storage server and present them as iSCSI targets to other servers
Applications for the Microsoft iSCSI Target
This is great stuff to ‘build your own' no-cost/low-cost SAN for development/test use, or even a production SAN if deployed thoughtfully on robust hardware. Many companies use and depend on Windows Storage Server 2008 R2 boxes that include the very same iSCSI Target 3.3 software that is now available for free to Windows server owners. What a great way to repurpose physical servers with large local storage, i.e., > 2-TB. Not much RAM is needed; even 2-GB RAM will do the job in a small environment. Microsoft has made their clustering and high-availability technologies that require a SAN much more accessible. Now anyone with a 1-GB network switch and some extra 1-Gbps Ethernet cards can have a fully functional SAN.
Real world test
This week a new development team member needed a Visual Studio VM in the lab. We cloned an existing development VM running Visual Studio 2010, that had been running as a Hyper-V guest with local VHD storage. The cloned VM was mounted in Hyper-V, with the disk (appearing to Hyper-V as a pass-through disk) actually provided by the iSCSI Initiator software on the Hyper-V host computer. A lead developer took delivery of the new VM and prepared the VM for the new user, checking everything out. After he was done, I chatted with him; he was happy with the result. I asked him if he noticed any performance issues and he said none at all-he had no idea the VM was running over 1-GB Ethernet iSCSI rather than local storage!
Cheap entry to private clouds
Consider repurposing physical servers without a lot of local storage as Hyper-V hosts, as long as they have 6-GB or more RAM; they may have a second career as iSCSI SAN-connected host nodes. Server hardware recently retired as part of technology refreshes might be great candidates to form that pre-production test environment you have needed for a while. A natural way to optimize your resources might be to consolidate most of your storage onto a few servers, and make them storage servers. Then consolidate CPU and RAM on other servers, and make them Hyper-V hosts. Voila, the core components of a private cloud.Disappointment
Hyper-V host backup is not supported. For application-consistent backups of Hyper-V virtual machines, you need to use a backup agent inside the VM (traditional backup). We also noted that mounted iSCSI volumes used by Hyper-V are also not backed up by DPM 2010, and require in-guest backup using a DPM agent or other software (such as Windows Backup to a different volume).Recommended next readings
- Microsoft iSCSI Software Target 3.3 for Windows Server 2008 R2 available for public download Jose Barreto, a member of the File Server team at Microsoft Corporation effectively communicates this announcement and provides a walk-through of the download and install of the iSCSI Target software.
- Step-by-step: Using the Microsoft iSCSI Software Target with Hyper-V Up and running fast with iSCSI Target and Hyper-V for your lab or proof of concept demo.