About iSCSI Boot
Updated: September 30, 2009
Applies To: Windows Server 2008 R2
The Microsoft® Internet SCSI (iSCSI) Initiator provides access to devices over an Ethernet network connection. iSCSI devices differ from network-attached storage devices in that iSCSI provides block-level access to disks via iSCSI rather than file-based access via a network-attached storage device. An iSCSI-connected disk is displayed in Disk Management and Windows Explorer as is any other disk drive.
Microsoft Internet SCSI (iSCSI) Boot enables you to start Windows Server®-based computers by using a network adapter or an iSCSI host bus adapter (HBA) as an alternative method of accessing block-level storage to local storage. This can help save both power consumption and heat generated by eliminating the need for local storage on each server or blade server.
When using iSCSI Boot with a network adapter, an iSCSI Boot Firmware Table (iBFT) is created in memory to expose information about the iSCSI connection so that Windows Setup is able to determine that the attached device is bootable.
We recommend that you deploy iSCSI Boot in Windows Server 2008 and Windows Server 2008 R2 environments by using a DVD installation of Windows Server while the server is connected to the iSCSI target device. Optionally, after you perform the first installation, you can capture the image and then deploy it on other servers that use the same network adapter.
In the first two scenarios of the following table, the boot device is still seen as a network adapter, not as a storage adapter.
Network adapter uses Pre-Boot Execution Environment (PXE) to connect to a third-party service and obtain an iBFT for booting. The computer boots by using Microsoft iSCSI Software Initiator.
Uses a network adapter that supports PXE booting to connect to a server such as netBoot/i from Double-Take to get the required information to connect to the iSCSI target device and boot, which is the iBFT.
Server network adapter creates iBFT for connection to iSCSI target without requiring external services.
Uses a network adapter that supports iSCSI Boot. This type of solution does not require additional software to obtain an iBFT.
The boot device is a true storage adapter and utilizes vendor-provided drivers to manage the network stack and connectivity to the iSCSI target device. When using this type of configuration, it is possible to upgrade the operating system to a new version if the HBA shows as a unique PCI device.
About the iSCSI iBFT
The iSCSI Bios Firmware Table (iBFT) is a table that is created in memory and enables the use of a network adapter as a boot device. The iBFT is used only with Scenarios 1 and 2 in the preceding table.
To boot from an iSCSI target disk in Scenarios 1 and 2 in the previous table, it is necessary that an iSCSI Boot Firmware Table (iBFT) be present in memory both during setup of Windows®, as well as on each restart of the system.
For Scenario 1, the iBFT is created by a third-party program, such as Double-Take netBoot/i, and then is transferred to the local computer via a PXE network boot connection.
For Scenario 2, the iBFT is created by the network adapter firmware, and can be seen by Windows Setup as a bootable device without requiring any additional software.
Some types of adapters are actually capable of operating in all three modes, depending on system firmware support and the specific driver that is installed. For these types of adapters, we recommend that you review the configuration with the hardware vendor to determine which boot methods are supported and available with the specific server in question.
The purpose of this document is to provide an overview of the first two scenarios to describe the configuration of iSCSI Boot on a Windows Server 2008 R2 system.
Prerequisites for using iSCSI Boot
This guide assumes that you have already completed the following:
Set up an iSCSI target and configured a disk for the Windows Server computer to use.
Configured a network adapter for the Windows Server 2008 computer to boot from the iSCSI target by configuring either a third-party provider’s iBFT or the network adapter firmware on cards that are capable of creating their own iBFT.
Installed the non-domain joined configuration that you want to image.
Requirements for iSCSI Boot deployment
This section details the requirements for deploying iSCSI Boot on Windows computers.
Windows versions iSCSI Boot is supported only on Windows Server. Client versions of Windows, such as Windows Vista® or Windows 7, are not supported.
Network requirements When you configure a server to boot by using iSCSI, you must have a dedicated network adapter on a dedicated network for iSCSI network traffic. At least one additional network port and adapter are required for all other network traffic.
After you install Windows Server using iSCSI Boot, the system depends on the same network adapter that was used during setup. If you change the network adapter, you are required to reinstall Windows Server.
iSCSI Boot configuration in Windows Server 2003 environments requires the use of a TCP/IP version 4 IP address (IPv4). To use IPv6 addresses with iSCSI Boot, you must use Windows Server 2008 or Windows Server 2008 R2.
The use of network filter drivers is not supported on the network adapter that is used for iSCSI Boot. Attempting to install software that requires a network filter driver on the iSCSI Boot network adapter may not be possible.
You cannot use network filter drivers on a network adapter that is used for iSCSI Boot. Software that requires a network filter driver may not function properly if it is targeted at the iSCSI Boot network adapter.
Depending on your Group Policy implementation, using Internet Protocol security (IPsec) with iSCSI Boot may not be possible unless the iSCSI target is also configured with IPsec.
Differences in Windows functionality when using iSCSI Boot
This section details the differences in functionality that you might experience when using iSCSI Boot, depending on your environment and configuration.
By default, a server that boots by using an iSCSI Boot network adapter does not have the ability to generate memory dumps. If memory dump creation is required, a driver must be obtained by the network adapter manufacturer if you are using a network adapter that creates an iBFT, or from the software vendor providing the iBFT via PXE solution.
On a Windows iSCSI Boot via a network adapter implementation, you cannot upgrade the version of Windows that is installed on the iSCSI device.
When you use an iSCSI HBA for iSCSI Boot, you can upgrade your version of Windows if the HBA presents itself to Windows as a separate PCI device.
When using iSCSI Boot, to start a server that is running Windows, you cannot use Sleep, Resume, or Hibernate .
Windows Server 2008 supports the use of Microsoft Multipath I/O (MPIO) with iSCSI Boot and a maximum of two connections for use at boot time. Windows Server 2008 R2 supports a maximum of 32 connections via MPIO at boot time.
Types of deployment discussed in this document
This document details deployment for Scenarios 1 and 2 as discussed in the previous section. Because systems that use an iSCSI HBA to boot are considered to be using a standard “storage” adapter, their deployment is handled the same way as it would be for a non-iSCSI Boot deployment that uses the Windows Automated Installation Kit (Windows AIK).
These scenarios can be deployed by using either a DVD installation of Windows directly from the installation media, or they may also be combined with Sysprep and image capture tools to deploy the image to a number of computers that will boot via iSCSI. When you perform an image deployment by using iSCSI, it is important to note that the network adapter used on the source computer where the deployment image is created must match the network adapter on the computers to which the image will be deployed.
We recommend that when you create an iSCSI Boot image, you perform the installation on a computer that is configured for iSCSI Boot and does not have any locally connected storage during the Windows installation. If local disks are present in the system, it may prevent boot files from being located on the correct disk, which would result in an unbootable image.
There are two primary methods of collecting an iSCSI Boot image for deployment to other iSCSI Boot systems:
Use Windows Preinstallation Environment (Windows PE) and ImageX (or another image-capture tool) to capture the image.
Install Windows Server on the computer by using iSCSI and Sysprep.
Mount the iSCSI disk on a different computer for the image capture and deployment, rather than booting from Windows PE to capture the image.
Copy the image to another disk to deploy to a second computer with the same type of network adapter.