Windows 7 : Preparing Disks for Use (part 1) - Creating Mirrored, Spanned, or Striped Volumes

Disk Management uses the same set of dialog boxes and wizards whether you are partitioning basic disks or dynamic disks. By default, the first three volumes on a basic drive are created automatically as primary partitions. If you try to create a fourth volume on a basic drive, the remaining free space on the drive is converted automatically to an extended partition with a logical drive that is the same size as the extended partition. Any subsequent volumes are created in the extended partitions as logical drives automatically.

In Disk Management, you create partitions, logical drives, and simple volumes on an internal or external hard disk drive by completing the following steps:

1. In Disk Management’s Graphical view, right-click an unallocated or free area and then choose New Simple Volume.

2. In the New Simple Volume Wizard, click Next.

3. On the Specify Volume Size page, shown in Figure 1, size the volume within the maximum and minimum size limits. If you want the volume to use all the space available, set the volume size equal to the value shown for the maximum disk space in MB. Click Next.

Figure 1. Setting the volume size

1. On the Assign Drive Letter or Path page, shown in Figure 2, use the “Assign the following drive letter” list to assign a drive letter to the volume, and then click Next.

NOTE

On most systems, the drive letter B and drive letters E through Z are available, with drive letter A reserved for a floppy disk, C assigned to the primary disk, and D assigned to the CD/DVD drive. If your computer has a secondary hard disk, a secondary CD/DVD drive, or both, you may find that drive letter E or the drive letters E and F are already assigned as well.

1. On the Format Partition page, shown in Figure 3, use the “File system” list to set the filesystem type. The options you have depend on the size of the volume and type of device, and they include FAT, FAT32, and NTFS. NTFS is selected by default in most cases. If you create a filesystem as FAT or FAT32, you can later convert it to NTFS. However, you can’t convert NTFS partitions to FAT or FAT32.

1. The “Allocation unit size” list sets the cluster size for the filesystem. A cluster is a logical grouping of file sectors. In most cases, you’ll want the “Allocation unit size” list to be set to Default. This allows Windows 7 to optimize the cluster size based on the volume size.

Figure 2. Assigning a drive letter

Figure 3. Setting the formatting options

NOTE

On the Windows operating system, most disk drives use a fixed sector size of 512 bytes, and because of this, a cluster is typically made up of multiple sectors. For example, if the cluster size is 4,096 bytes, there will be four 512-byte file sectors per cluster. If you create large quantities of small files, you might want to use a smaller cluster size, such as 512 or 1,024 bytes. With these settings, small files use less disk space. With that said, it is important to point out that the disk drive industry is transitioning to large-sector disks. See http://support.microsoft.com/kb/923332/en-us for more information.

1. The “Volume label” text box sets a text label for the volume. By default, the label is set to “New volume.”

2. The “Perform a quick format” checkbox allows Windows 7 to format the volume without checking the partition for errors. Although this option can save you a few minutes, it’s usually better to allow Disk Management to check for errors and mark any bad sectors it finds on the disk so that they aren’t used.

3. The “Enable file and folder compression” checkbox turns on compression for the disk. Built-in compression is available only for NTFS. If you select this option, files and folders on the volume are compressed automatically.
   

4. Click Next and then click Finish. Disk Management will create and format the new volume.

1. Creating Mirrored, Spanned, or Striped Volumes

When you are partitioning and formatting disks in Disk Management, you can create mirrored, spanned, and striped volumes. If you have unallocated space on two or more disks of the same type, either basic or dynamic, you can combine this space to create a mirrored volume, a spanned volume, or a striped volume.

With mirrored volumes, you combine identically sized volumes on two different drives to create a redundant data set. Because the drives are written with identical sets of information, you can still obtain the data from the other drive if one of the drives fails. Although disk mirroring offers fault tolerance, the key drawback is that it effectively cuts the amount of storage space in half. For example, to mirror a 750 GB volume, you need another 750 GB volume. That means you use 1,500 GB of space to store 750 GB of information.

With spanned volumes, the only benefit is being able to combine multiple disks to create a single volume. Files are written to the entire spanned volume randomly and there are no read/write benefits. There is a huge downside, however. If any disk in a spanned volume fails, the entire volume fails as well, and all data will be lost.

NOTE

Although you can only create mirrored volumes on dynamic disks, Windows 7 will allow you to initiate mirroring on basic disks. Here’s how this works: if your computer has free space on multiple disks, you’ll be able to right-click an unallocated area and then choose New Mirrored Volume. When you complete the creation process and click Finish, you’ll see a warning prompt telling you that the operation you selected will convert the selected basic disks to dynamic disks. You are also asked whether you are sure you want to continue. If you click Yes, Disk Management will convert the disks and then mirror the volumes. If you click No, you’ll cancel the conversion process and the mirrored volume will not be created.

With striped volumes, you also can combine multiple disks to create a single volume. You get faster read/write access to data because data is read from and written to multiple disks. For example, with a three-disk striped volume, data from a file will be written to Disk 1, then to Disk 2, and then to Disk 3 in 64 KB blocks. However, like a spanned volume, a striped volume has no fault tolerance. If any disk in a striped volume fails, the entire volume will fail as well, and all data will be lost. Additionally, although you can extend simple and spanned volumes to increase their volume size, you cannot extend striped volumes.

In Disk Management, you create mirrored, spanned, or striped volumes by completing the following steps:

1. In Disk Management’s Graphical view, right-click an unallocated area and then choose New Mirrored Volume, New Spanned Volume, or New Striped Volume as appropriate. When the wizard starts, click Next.

2. On the Select Disks page, shown in Figure 4, available disks are shown in the Available listbox. Select a disk in this listbox and then click Add to add the disk to the Selected listbox. If you make a mistake, you can remove disks from the Selected listbox by selecting the disk and then clicking Remove.

3. The “Maximum available space” text box shows you the largest area of free space that can be used on a selected disk; the “Total volume size” text box shows you the total disk space currently allocated to the volume.

4. Specify the space that you want to use on each disk by selecting each disk in the Selected listbox and then using the “Select the amount of space in MB” listbox to specify the amount of space to use on the selected disk. Although spanned volumes can use all available space on any selected disk, mirrored, and striped volumes must use an equal amount of space on each disk. Click Next.

5. Follow steps 4–10 in the preceding section.

Figure 4. Selecting the disks to span or stripe