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== Creating a Mirrored (RAID 1) Volume from the Command Prompt ==
Windows Server 2008 Mirrored (RAID 1) volumes may also be created from the command prompt using the '''diskpart''' tool. This may be launched either from a command prompt window, or from the Run dialog simply by entering ''diskpart'' at the prompt. Once invoked the ''DISKPART>'' prompt will displayed, ready to recieve receive commands.
The first step in creating a mirrored set using diskpart is to identify the disks to be used. This can be achieved using the ''list disk'' command:
For the purposes of this tutorial we will be creating a mirrored volume based on a set consisting of disks 1 and 2. The mirrored volume is created by first creating a simple volume on the first disk and then adding a second disk to the mirrored set.
The first volume is created using the ''create volume'' command combined with the ''disk='' directive. The size of the volume may also be specified using the ''size='' directive. Omission of the ''size='' option will cause diskpart to create volume which occupies all the availabel available space on the designated disk. For example:
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Once formatted, the last task is to assign either a drive letter or mount point to the volume by which it will be accessed:
To assign a drive letter:
== Adding a Mirror to an Existing Volume ==
A mirror may be added to an existing volume using either the Disk Managament Management snap-in, or from the command-prompt using the '''diskpart''' tool. When a mirror is added to an existing volume Windows creates a second volume equal in size and file system type on a second disk of your choice and copies (a process also known as ''resynching'') the data on the existing volume to the mirror.
To mirror to an existing volume using Disk management, right click on the existing volume in the graphical view and select ''Add Mirror'' to invoke the ''Add Mirror'' dialog shown below:
The above dialog will list disks eligable eligible to act as a mirror for the existing volume. Select the desired disk and click on ''Next''. A warning dialog may appear notifying you of any additional changes that may be made as a result of the addition (such as converting basic disks to dynamic disks). Click ''Yes'' to proceed. The resynching process will now begin, the progress of which will be displayed in the graphical view.
To add a mirror to an existing volume from the command prompt, start diskpart and identify the existing volume using the ''list volume'' command:
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From the above information it is clear that Volume 2 is 8189 Mb MB in size. In order to be able to mirror this volume, a disk with at least 8189 Mb MB is required. Clearly, disk 2 meets this requirement. Therefore, all that needs to be done is to add disk 2 as the mirror disk for our volume using the ''add disk'' command. Note that if the disks are not dynamic disks they will need to be converted with the ''convert dynamic'' command:
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== Breaking and Removing Mirrored Sets ==
A Windows Server 2008 mirror may be broken (which creates two separate and independent volumes containing identical data) or removed (which removes the data on the mirror leaving free space on the designated mirror disk).
To break a mirror from the Disk Management snap-in right click on one of the volumes in the set in graphical view and select ''Break Mirrored Volume'' from the pop-up menu.
If one of the disks in a mirrored set fails the good news is that, unlike striped volumes, all the data is still present on the remaining healthy disk (this, after all is the whole point of disk mirroring). In this situation, however, it is important to replace the faulty disk and rebuild the mirror before the healthy drive also fails.
To achieve this right click on the failed volume and select ''Remove Mirror''. Next, identify a suitable alternate or newly installed drive with sufficient space to act as a mirror. Right click on the existing, healthy volume from the original mirrored set, select ''Add Mirror'' from the resulting menu, select the new disk in the ''Add Mirror'' dialog and click on ''Add Mirror''. Windows will now rebuild the mirror using space on the new disk. As noted above , this process can take some time depending on the size of the volume in question.
