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== An Overview of GPT and MBR Partition Styles ==
Before a Windows Server 2008 system disk can be mirrored it is important to identify the partition style used by the disk as this will dictate the technique used to create the mirror. In order for a disk to be used to store data it must first have partitions created on it. These partitions are then formated formatted with a particular file system (FAT, FAT32, or NTFS) and used either as a basic disk or as dynamic disk. Obviously, the operating system needs some mechanism for organizing and managing these disk partitions and Windows Server 2008 provides two such partitioning styles known as Master Boot Record (MBR) or GUID Partition Table (GPT).
The MBR style was originally developed for x86-based computer systems and is by far the most common style in use at present. GPT, on the other hand, was originally developed for 64-bit Itanium based systems. With the arrival of Windows Server 2008 both x86 32-bit and 64-bit systems support MBR and GPT partition styles. It is important to note, however, that 32-bit systems can only boot from MBR disk partitions and 64-bit systems can only boot from GPT partitions.
== Mirroring Boot and System Volumes on an MBR Disk using Disk Management ==
The process of mirroring boot and system volumes on Windows Server 2008 MBR disks is considerably more straightforward than on GPT disks. For the purposes of this chapter we will be working with a system containing 2 two disk drives. Disk 0 is the system disk and disk 1 is an unallocated disk installed for the purpose of mirroring the system disk. This process can be performed using either the Disk Management interface or from the command prompt using the '''diskpart''' tool (covered in the next section). The Disk Management interface can be accessed either from the Server Manager or Computer Management tools. To launch the Server Manager, open the Start menu and click on the Server Manager option, or click on the Server Manager icon in the task bar. Alternatively launch Computer Management from Start -> All Programs -> Administration Tools -> Computer Management or run '''compmgmt.csc''' at the command prompt or in a Run dialog.
Before the system disk can be mirrored it must first be converted to a dynamic disk. To achieve this right click on the system drive in the Disk Management graphical view, select ''Convert to Dynamic Disk...'' from the popup menu and follow the instructions in the resulting dialog to perform the conversion.
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In the above output disk 0 is the current system disk and disk 1 is the disk to be used as the shadow system disk. If the disks are not yet dynamic they need to be converted before the remainder of the mirroring set up and can be completed:
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In the above output, Partitions 1 and 3 are the EFI and MSR partitions respectively. In order to accurately mirror the system disk these partitions also need to created on the mirror disk using the ''create partition'' command using and the '''efi''' and '''msr''' options as follows:
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This will initiate the mirroring process which may take some time depending on the size of the system volume as Windows Server 2008 carries out the resynching process. In addition to resynching the mirrored volumes Windows will also add the mirrored disk to the boot configuration such that it will be listed as the ''Microsoft Windows Server 2008 - secondary plex'' option on the boot menu next time the system is booted.

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