Converting Basic Disks to Dynamic Disks

Up to this point everything that has been discussed in this article has related to Basic disks, but Windows XP professional supports another type of disk structure called a Dynamic disk. Dynamic disks first appeared in Windows 2000 and are only compatible with Windows 2000 and Windows XP Professional operating systems. If you're running Windows XP Home Edition the option for Dynamic disks is unavailable.

Throughout this article we've spent a substantial amount of time talking about primary partitions, extended partitions, and logical drives. A Dynamic drive contains dynamic volumes rather than partitions, making it possible to have an unlimited number of logical drives. Another big difference between basic and dynamic disks is there is no Master Boot Record (MBR) on a dynamic disk. Instead, it stores the layout of the disk volumes in a database stored on the last 1 MB of the disk.

Other than the fact dynamic volumes are used instead of partitions, why would you consider creating or converting a basic disk to a dynamic disk? Dynamic disks allow you to create a number of different disk structures that aren't available on basic disks. For example;

• Simple Volume - A dynamic volume that's composed of disk space from a single dynamic disk. Not fault-tolerant but can be mirrored.
• Spanned Volume - A dynamic volume that uses disk space on more than one physical disk. If there is more than one dynamic disk the size of the spanned volume can be increased by extending it onto the additional dynamic disk.
• Striped Volume - A dynamic volume that stores data in stripes across two or more physical hard drives. Striped volumes are noted for very fast performance but the downside, which can be substantial, is that if one of the disks in the stripe set fails the entire volume is lost.
• Mirrored Volume - A volume that duplicates the data on two physical disks. The identical volumes are called mirrors. Since the data is mirrored on a different disk, if one disk fails the system will switch to the mirror and remain functional. Mirrored volumes are also fault-tolerant.
• RAID-5 Volume - This is a bit of a departure from the other types of volumes in that it requires at least three hard disks to implement, but basically it consists of data and parity sets that are striped across multiple hard disks. If one of the disks in a RAID-5 volume fails, XP can recreate the failed portion by using the data and parity information from the remaining disks in the volume.

I'll be the first to tell you that dynamic disks aren't for everybody. They have a learning curve and the chances of screwing something up is substantially higher than working with basic disks. Because some of the most useful disk structures require multiple hard drives there is the additional expense as well as the risk associated with data loss in case of a drive failure. A comprehensive backup strategy to media that can handle the size of data sets that are created is essential. Until you've experimented with dynamic disks to learn and understand their uniqueness I wouldn't recommend they be used to the exclusion of basic disks.

For those that do want to experiment, the screen captures below illustrate converting Disk 2 and 3 into a Spanned Volume.

Right click on one of the Basic Disks to be converted to a Dynamic Disk and select [Convert to Dynamic Disk] to proceed.

Fig. 01

Select the disk or disks to be converted. In this example I'm selecting two because they will ultimately become a Spanned Volume. Click [OK] to proceed.

Fig. 02

Compare Fig. 03 to Fig. 01 and note the Basic disks have been converted to Dynamic disks. Right click in the Unallocated space and select [New Volume...] to open the New Volume Wizard.

Fig. 03

The New Volume Wizard is the Dynamic Disk equivalent of the New Partition Wizard for Basic Disks, reflecting the difference that Dynamic Disks use volumes rather than partitions. Click [Next] to proceed.

Fig. 04

The Volume Type box contains three choices; Simple, Spanned, and Striped. I've included screen captures [Fig. 05, 06, and 07] of the window showing each option selected so the Description section is available for reading.

Fig. 05

Fig. 06

Fig. 07

Because I'm creating a Spanned Volume the Select Disks screen appears listing the disks that are available to become a part of the volume. In this case, Disk 2 is selected by default and the additional choices available are shown in the Available pane.

Fig. 08

Once the disks have been added, select the amount of space to be allocated to the Spanned Volume and click [Next] to proceed.

Fig. 09

Disk Management automatically offers to assign the next available drive letter to the new partition. Use the drop down selector to choose a different letter.

Fig. 10

The final step is to select the formatting options for the volume. It's not absolutely necessary to format the volume if you're just setting up a partition scheme that will be used later. If so, select the first option. If the volume is formatted at this time the drop down boxes are used to select the file system type and allocation unit size. Unless you have a specific reason reason to use FAT32 or change the allocation unit the defaults will work fine. Supply a label for the volume now (I used Spanned Example) or just accept the default. If you want to save some time use the quick format option.

Fig. 11

Review the selected settings [Fig. 12] and click the [Finish] button. The process will begin immediately with no further user intervention.

Fig. 13

As Fig. 14 illustrates, the Spanned Volume, Spanned Example, has been created and added to Disk Management, assigned drive letter H and is formatted with the NTFS file system. Looking at the spanned volume in the lower half of the Disk Management utility is a bit misleading because it shows both Disk 2 and 3 as being 19.08 GB, and although this is true, both disks are now under one drive letter (H) and the total spanned capacity of the two drives is 38.16 GB as shown in the upper part of the Disk Management display.

Fig. 14

Before you do anything with Dynamic disks I suggest you read through the entire Help section of Disk Management. There are many little caveats to working with them that are far beyond the scope of this brief introductory article. Even if you absorb every word of the Help section you'll likely end up making some mistakes that only experience will solve, but it's always better to go into a new area with as much knowledge as possible.