Issues Involved In Converting Basic Disks To Dynamic Disks

by [Published on 21 July 2005 / Last Updated on 21 July 2005]

One of the Windows Server 2003 features that I’ve always found most useful is the ability to convert basic disks to dynamic disks. The advantage of doing this is that the Windows operating system allows you to span a single volume across multiple dynamic disks. By spanning a volume across multiple disks, you can create a larger volume than what a single disk can hold, you can achieve better performance than what a single disk would provide you with, and you can even achieve a degree of fault tolerance against hard disk failure. Even with all of these benefits, there are some serious issues that you need to be aware of before you even think about converting a basic disk into a dynamic disk. In this article, I will discuss these issues.

Before I Begin

Before I get started, there is one thing that I want to get out of the way up front. I know that some of the people who are reading this got here because they did an Internet search on how to convert a basic disk into a dynamic disk. If you are one of those people, then I’m assuming that you will probably skip to the instructions at the end of the article. Before you do though, there is one extremely important thing that you need to know about the conversion process. Converting a basic disk into a dynamic disk is a semi-permanent operation.

Once you convert a basic disk into a dynamic disk, you can not convert it back into a basic disk unless you delete every volume on the entire disk. There is no way to convert a dynamic disk into a basic disk and preserve the drive’s contents. You will have to make a backup of the data prior to the conversion, delete the volume, convert the disk to basic, create a partition, assign the partition a drive letter, and restore your backup.

Not Every Hard Disk Can Be Converted

Now that I’ve explained the most important detail about the conversion process, let’s move on to rule number two. This rule is that not every basic hard disk can be converted to a dynamic disk. Most of the rules regarding which disks can and can’t be converted are common sense.

For example, removable media, such as ZIP disks and Jaz disks, can’t be converted into dynamic disks. The reason for this is simple. A dynamic disk can span multiple drives. If a volume spanned a removable disk and the disk was removed from the system, then the volume would be broken.

Another situation in which a basic disk can’t be converted into a dynamic disk is if the basic disk exists on a laptop computer. There are a few different reasons for this. First, you really shouldn’t be running Windows Server 2003 on a laptop anyway. Second, most laptops only have one hard drive. A system with a single hard disk would not gain any benefit from using dynamic disks. Third, usually when a laptop does have multiple hard drives, one of those drives is in a docking station. This goes back to the whole removable media thing. If you remove your laptop from the docking station then a dynamic disk volume that spanned the laptop’s internal hard drive and the docking station’s hard drive would be broken.

The third situation in which a basic disk can’t be converted into a dynamic disk involves clustered servers. If Windows Server 2003 Enterprise Edition or Datacenter Edition is configured as a cluster, then the shared storage system can not be configured as a dynamic disk.

The final rule about basic disks that can’t be converted is that you can’t convert any hard disk with a sector size greater than 512 bytes (this isn’t something that you are likely to run into). You can have cluster sizes greater than 512 bytes, just not sectors.

Conversion is Not a Quick Fix

Now that you know what types of hard disks you can and can’t convert from basic to dynamic, I want to explain that the conversion process is not intended as a quick fix for space issues. A real life example of this happened to an administrator that I used to know. One of the partitions on his server started to run a little low on disk space. Since he had some free space on another hard disk, he decided to convert both disks into dynamic disks so that he could extend the volume onto the hard disk that had the free space.

This sounds logical enough, but there is a problem with it. The volume that was low on space began life as a partition on a basic hard disk (basic disks use partitions, dynamic disks use volumes). If a volume was originally a partition on a basic disk then that volume can not be extended or spanned. Only volumes that are created on dynamic disks can be extended or spanned.

Other Oddities

By now, your head is probably spinning with all of the rules about what you can and can’t do with dynamic disks. There are a few more repercussions that you need to know about though.

For starters, you can not install Windows Server 2003 onto a native dynamic volume. If your server contains a partition on a basic disk and you convert that disk into a dynamic disk, then you will be able to install Windows Server 2003 on the resulting volume because that volume began life as a partition on a basic disk. If however, you create a brand new volume on a dynamic disk, then Windows Setup will not allow you to install Windows onto that volume.

Another thing that you need to be aware of is that if you convert a basic disk to a dynamic disk, then the conversion will not actually occur yet if files in the disk are open. If files are open, then the conversion will require you to reboot your system. That way, files are closed and the conversion can happen during the reboot. A reboot is always necessary if you are converting the disk containing the server’s operating system, but is only required for other conversions if there are open files.

The last oddity that you need to be aware of is that dynamic disks are not recommended for servers containing multiple operating systems. If your server contains multiple operating systems then the only operating systems that will be able to access dynamic disks (locally, I’m not talking about over the network) are Windows 2000 Server and Windows Server 2003. If you have some other operating system installed and it happens to reside on a dynamic disk, you won’t even be able to boot that operating system.

Making the Conversion

Converting a basic disk into a dynamic disk is simple. To do so, enter the DISKMGMT.MSC command at the server’s Run prompt. When the Disk Management console opens, right click on the hard disk that you want to convert (right click on the hard disk itself, not on a partition). Now, select the Convert to Dynamic Disk command from the shortcut menu. You will now be prompted as to which disk you want to convert. Verify that the correct hard drives are selected and click OK. You will now see a very similar screen to the last one, but this one also displays logical drive information. Verify once again that the correct hard drives are selected and click OK.  You will now see one last “Are You Sure” message. Click Yes and the disk will be converted.

Conclusion

As you can see, converting a basic disk into a dynamic disk is simple. However, this simple conversion has some major implications. I recommend giving some serious thought to the consequences of your actions prior to making the conversion.

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