In another case of Microsoft making an internal piece of software commercially available, the company has shipped...
The Microsoft iSCSI Software Target designed to work with Windows Server 2008 R2. The new version is a software protocol that allows SCSI commands to be routed over networks, permitting a disk hosted on a remote network-connected piece of hardware to be seen locally. In essence, it helps establish storage area networks.
Software Target helps set up virtual hard disks in VHD format and to use them as iSCSI targets for remote servers. Users can also take snapshots of those virtual disks, mount them locally for read-only or read-write access and perform a whole slew of other powerful management and system-protection functions.
One of the major applications for Software Target is using it with Hyper-V, where it can be used in lieu of a passthrough disk or other local media. A slew of PowerShell cmdlets also come as part of the MicrosoftIscsiTarget module. Jose Barreto has published a detailed how-to guide for using Software Target to create a differencing VHD that can serve as an OS boot drive.
If Software Target is so useful, why wasn't it released earlier for the public? Actually, it was—just not as a standalone item. It was originally confined to being part of Windows Storage Server circa 2007, in large part because it was a valuable complement to the things Storage Server was meant to accomplish.
I'm assuming an important reason the product was kept so close to the vest was Microsoft wanted to get as much testing done and receive as much feedback as possible among Windows Storage Server users before releasing it to a much wider set of users. In Barreto's blog post describing the release, he talks about the testing revolving around the use of Hyper-V and Windows Server Failover Clusters because, "they are among the most common deployment scenarios."
Software Target arrives as a single downloadable .EXE file, which unpacks itself into a specified folder when it is run for the first time. In that folder there are release notes and a Getting Started guide (in a subfolder labeled "Documentation") and MSIs to install both Software Target and the VSS/VDS providers. Details on configuring the Target are available there, but have also been discussed online at Barreto's blog and in the official Microsoft documentation.
There are some limitations of Software Target users should be aware of before deploying it anywhere.
- Previous versions of Windows Server are not supported. Windows Server 2008 R2 or later must be used.
- Software Target can't be used in conjunction with the "Core" installation option for Windows Server 2008 R2. Only full server installs will work.
- There is no 32-bit version of Software Target. (Consider it standard operating procedure that all Windows Server components are 64-bit only.) There are however, 32- and 64-bit VSS and VDS providers.
- iSCSI requires a great deal of bandwidth. For the best results users should dedicate a physical network segment of the fastest possible media to any iSCSI traffic. Don't try to run iSCSI over the same network fabric used for accessing servers.
- Don't try to use the conventional volume-shadow tools (Vssadmin.exe or Vshadow.exe) to modify snapshots created with Software Target. Software Target has controls that are part of its own console for dealing with snapshots; use those tools instead.
Microsoft has a list of a few other general issues relating to disk sizes (e.g., users are unable make a parent VHD larger than 1.99TB) and clustering listed in their documentation. Read them thoroughly before attempting any production deployments.
ABOUT THE AUTHOR
Serdar Yegulalp has been writing about personal computing and IT for more than 15 years for a variety of publications, including (among others) Windows Magazine, InformationWeek and the TechTarget family of sites.