Creating and Managing Simple and Spanned Volumes on Windows Server 2008

So far in this book we have worked primarily with basic disks. Simple and spanned volumes in Windows Server 2008 take advantage of a concept known as dynamic disks. In this chapter of Windows Server 2008 Essentials the topic of using dynamic disk support to create both simple and spanned volumes on Windows Server 2008 system will be covered in detail.

An Overview of Dynamic Disks

As covered in the preceding chapters, basic disks allow partitions to be created on a physical disks which are subsequently formatted with a particular file system and then used to store data. Whilst the partitions on a basic disk can be increased in size this can be achieved within the confines of the space available on the physical disk on which they reside.

Dynamic disks bring significantly more flexibility into the creation and management of volumes both in terms of space management, performance and redundancy. There are five types of dynamic volume which can be created through the use of dynamic disks:

• Simple Volume - The equivalent of a partition on a basic disk. A simple volume must reside on a single disk and cannot be extended beyond the space available on that disk.

• Spanned Volume - A spanned volume can span multiple physical disk drives or be comprised of multiple, non-contiguous volumes on a single disk drive. Spanned volumes avoid many of the limitations inherent in simple volumes.

• Striped Volume - Also referred to as RAID 0, disk striping involves splitting data into multiple parts and writing each part to a different disk drive (a process which is reversed when the data is read back). The disks involved in this process are referred to as a stripe set. The key purpose of striping is to increase disk performance.

• Mirrored Volume - Also referred to as RAID 1, disk mirroring involves writing the same data to two drives such that if one drive fails an exact copy of the data is available on the second disk. The primary purpose of disk mirroring is data redundancy and disaster recovery.

• RAID 5 Volume - RAID 5 is a variation of volume striping. With RAID 5 striping is used in conjunction with parity error checking such that the data can continue to be used in the event that one of the drives fails. The parity information can also be used to restore data in the event of a failure using a technique known as regeneration. RAID 5 requires 3 or more disks and is designed to provide fault tolerance.

Converting Basic Disks to Dynamic Disks with Disk Management

Windows Server 2008 allows basic disks to be converted to dynamic disks using the Disk Management interface. Before covering the steps to perform such a conversion there are a number of rules which need to be observed.

In the first instance, MBR disks must have at least 1Mb of free space at the end of the disk where the dynamic disk database will be stored. Both Disk Management and diskpart allocate this space automatically so this will only be a problem if the disk was partitioned using a third party tool or a n oder version of Windows.

GPT disks can only be converted if they have contiguous, Windows compatible partitions. It is not, for example, possible to convert a basic GPT disk containing one or more Linux partitions to a dynamic disk.

Finally, basic disks with sector sizes in excess of 512 bytes cannot be converted to dynamic disks.

Assuming that the above requirements are met, the first step is to open the Disk Management interface. This can be achieved by running compmgmt.msc in command prompt window or Run dialog and selecting Storage -> Disk Management.

To perform the conversion simply right click on the icon for the drive in question and select Convert to Dynamic Disk... from the popup menu.