Simple volumes are the dynamic-disk equivalent of the primary partitions and logical drives found on basic disks. When creating simple volumes, keep these points in mind:
If you have only one dynamic disk, you can create only simple volumes.
You can increase the size of a simple volume to include unallocated space on the same disk or on a different disk. The volume must be unformatted or formatted by using NTFS. You can increase the size of a simple volume in two ways:
- By extending the simple volume on the same disk. The volume remains a simple volume, and you can still mirror it.
- By extending a simple volume to include unallocated space on other disks on the same computer. This creates a spanned volume.
If the simple volume is the system volume or the boot volume, you cannot extend it.
From Microsoft TechNet