The iSCSI protocol is becoming increasingly popular in enterprise environments of all sizes. If you haven't heard of iSCSI, it’s simply an adaption of the tried-and-true SCSI protocol used to connect servers to high-performance disk enclosures and CD-ROM drives. It uses TCP/IP over wired networks instead of dedicated cables. (Remember all those thick cables and huge plugs with delicate pin-outs?)
In recent months, iSCSI has become wildly popular in part because of the rise of virtualization, especially virtualization technology that allows running virtual machines (VMs) to be moved between different servers so that maintenance can be carried out on the host server without affecting the availability of the guest VMs. The only interconnectivity required between servers and the disks on storage subsystems is an IP network, which allows many servers to share the same storage subsystem. With older technologies, such as SCSI DAS, two servers at most could access a shared storage subsystem. Fibre Channel (FC)-based SANs can be built to permit multiple servers to access the same storage subsystem. But FC-based SANs are extremely expensive and require special HBAs to be installed on servers before the servers can connect to FC controllers, which are specialized switches that are fronting a SAN.
Using an IP network, iSCSI costs far less than the alternatives and offers more flexibility. You might already be using NAS in your environment. NAS uses common IP-based protocols, such as WWW Distributed Authoring and Versioning (WebDAV), NFS, Server Message Block (SMB) and Common Internet File System (CIFS), but these protocols are file-level protocols and are generally not up to the task of providing access to extremely large files, nor are they suited for high-performance solutions such as virtualization or databases. The block-level iSCSI protocol avoids performance and other problems associated with file-level protocols, including file locking.
A number of vendors offer a wide range of iSCSI solutions today, including NAS systems with iSCSI support. Microsoft recently released Windows Storage Server 2008 R2, which is an optimized version of Windows Server 2008 R2, with iSCSI support. Available in storage products from vendors like Dell, HP, and others, Storage Server boasts an impressive range of features that allow you to build storage subsystems. Those subsystems can be used to host the virtual disks of your VMs, host huge databases for your database servers, and do pretty much anything else you can think to throw at them. Storage Server also includes easy-to-use management features and deduplication software to minimize storage requirements. Best of all, Storage Server integrates seamlessly into your Windows network and also offers support for typical NAS protocols.
In this article, I’ll describe how to set up and test Storage Server Enterprise Edition in your environment. Storage Server comes in Workgroup Edition, Standard Edition, and Enterprise Edition. An overview of the differences between each edition can be found at the Microsoft TechNet web page. Although Storage Server is only available for use in production environments in products from OEMs, if you have a TechNet subscription, you can download Storage Server as an update to Server 2008 R2. You can then test it in a physical or virtual environment. Click here for more details about downloading and using Storage Server.