iSCSI Target Boot Overview
Published: February 29, 2012
Updated: February 29, 2012
Applies To: Windows Server 2012
iSCSI Target Server enables you to network boot multiple computers from a single operating system image that is stored in a centralized location. This improves efficiency, manageability, availability, and security. iSCSI Target Server in Windows Server 2012 can boot hundreds of computers by using a single operating system image and it provides the following benefits:
By using differencing virtual disks, you can use a single operating system image (the “golden image”) to boot up to 256 computers. As an example, in a deployment of Windows Server 2008 R2 HPC edition, the operating system image is approximately 20 GB. A common deployment is to have two mirrored disk drives that act as the boot volume. Rounding the operating system storage to 40 GB per instance, you would need approximately 10 TB of storage — for only the operating system image—to boot 256 computers. With iSCSI Target Server, however, you will use 40 GB for the operating system base image, and 2 GB for differencing virtual hard disks (VHDs) per server instance, totaling 552 GB for the operating system images. This provides a savings of over 90% on storage for the operating system images alone.
Controlled operating system images make it more secure and easy to manage. Some enterprises require that data be secured by physically locking storage in a centralized location. In this scenario, servers access the data remotely, including the operating system image. With iSCSI Target Server, administrators can centrally manage the operating system boot images, and control which applications to put in the golden image.
Rapid deployment. Because the golden image is a sysprepped operating system image, when the computers boot from the golden image, they skip the file copying and installation phase that occurs during Windows Setup, and they go straight to the customization phase. In Microsoft internal testing, 256 computers were deployed in 34 minutes.
Fast recovery. Because the operating system images are hosted on the iSCSI Target Server computer, if the diskless client needs to be replaced, the new computer can point to the operating system image, and boot up immediately.
A SAN boot is a solution that has been offered from various vendors. In Windows Server 2012, the iSCSI Target Server provides this network boot capability on commodity hardware.
iSCSI Target Server does not require special hardware for functional verification. In data centers with large-scale deployments, the design should be validated against specific hardware. For reference, Microsoft internal testing indicated that for a 256-iSCSI boot deployment, 24x15k-RPM (revolution per minute) disks in a RAID 10 configuration were required for storage. A network bandwidth of 10 GB is optimal. A general estimate is 60 iSCSI boot servers per 1 GB network adapter. However, an iSCSI boot-capable network adapter is not required for this scenario. If the network adapter does not support it, a software boot loader can be used (such as iPXE open source boot firmware).
iSCSI Target Server can be installed as part of the File and iSCSI Services role service in Server Manager.
For automation, you can use the corresponding Windows PowerShell cmdlets.