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Dynamic Volumes

With dynamic disks, you are no longer limited to four volumes per disk (as you are with basic disks). You can install Windows Server 2008 onto a dynamic volume; however, these volumes must contain the partition table (which means that these volumes must have been converted from basic to dynamic under Windows Server 2008, Windows Server 2003, Windows XP Professional, or Windows 2000). You cannot install Windows Server 2008 onto dynamic volumes that you created directly from unallocated space. Only computers running Windows XP Professional, the Windows 2000 family of operating systems, the Windows Server 2003 family of products, or the Windows Server 2008 can access dynamic volumes. The five types of dynamic volumes are

  • Simple
  • Spanned
  • Mirrored
  • Striped
  • RAID-5

Windows Server 2008 supports all five dynamic volume types. You must be a member of the local Administrators group or the backup operators group, or you must have the proper permissions delegated to you (if you are working within an Active Directory environment) to create, modify, or delete dynamic volumes.

Simple Volumes

A simple volume consists of disk space on a single physical disk. It can consist of a single area on a disk or multiple areas on the same disk that are linked together. To create a simple volume, follow these steps:

  1. Open Disk Management.
  2. Right-click the unallocated space on the dynamic disk where you want to create the simple volume and then click New Volume.
  3. Using the New Volume Wizard, click Next, click Simple, and then follow the instructions and answer the questions asked by the wizard.

Here are some guidelines about simple volumes:

  • You can create simple volumes on dynamic disks only.
  • Simple volumes are not fault tolerant.
  • Simple volumes cannot contain partitions or logical drives.
  • Neither MS-DOS nor Windows operating systems other than Windows Server 2008, Windows Server 2003, Windows XP Professional, and Windows 2000 can access simple volumes.

Spanned Volumes

A spanned volume consists of disk space from more than one physical disk. You can add more space to a spanned volume by extending it at any time. To create a spanned volume, follow these steps:

  1. Open Disk Management.
  2. Right-click the unallocated space on one of the dynamic disks where you want to create the spanned volume and then click New Volume.
  3. Using the New Volume Wizard, click Next, click Spanned, and then follow the instructions and answer the questions asked by the wizard.

Here are some guidelines about spanned volumes:

  • You can create spanned volumes on dynamic disks only.
  • You need at least two dynamic disks to create a spanned volume.
  • You can extend a spanned volume onto a maximum of 32 dynamic disks.
  • Spanned volumes cannot be mirrored or striped.
  • Spanned volumes are not fault tolerant.

Extending Simple or Spanned Volumes

Simple volumes are the most basic volumes on dynamic disks. If you extend a simple volume to another dynamic disk, it automatically becomes a spanned volume. You can extend a simple volume to make it a spanned volume, and you can also further extend a spanned volume to add disk storage capacity to the volume. You cannot extend a mirrored volume. Take these steps to extend a simple or a spanned volume:

  1. Open Disk Management.
  2. Right-click the simple or spanned volume you want to extend, click Extend Volume, and then follow the instructions and answer the questions asked by the Extend Volume Wizard.

You should be aware of the many rules about extending a simple or a spanned volume:

  • You can extend a volume only if it contains no file system or if it is formatted using NTFS. You cannot extend volumes formatted using FAT or FAT32.
  • After a volume is extended onto multiple disks (spanned), you cannot mirror the volume, nor can you make it into a striped volume or a RAID-5 volume.
  • You cannot extend boot volumes, system volumes, striped volumes, mirrored volumes, or RAID-5 volumes.
  • After a spanned volume is extended, no portion of it can be deleted without the entire spanned volume being deleted.
  • You can extend a simple or a spanned volume only if the volume was created as a dynamic volume under Windows Server 2003 or Windows Server 2008. You cannot extend a simple or spanned volume that was originally converted from basic to dynamic under Windows 2000 or Windows XP Professional.
  • You can extend simple and spanned volumes on dynamic disks onto a maximum of 32 dynamic disks.
  • Spanned volumes write data to subsequent disks only as each disk volume fills up. Therefore, a spanned volume writes data to physical disk 0 until it fills up, then it writes to physical disk 1 until its available space is full, then it writes to physical disk 2, and so on. However, if just one disk fails as part of the spanned volume—all the data contained on that spanned volume is lost.

Striped Volumes

A striped volume stores data in stripes on two or more physical disks. Data in a striped volume is allocated alternately and evenly (in stripes) to the disks contained within the striped volume. Striped volumes can substantially improve the speed of access to the data on disk. Striped volumes are often referred to as RAID-0; this configuration tends to enhance performance, but it is not fault tolerant. To create a striped volume, follow these steps:

  1. Open Disk Management.
  2. Right-click unallocated space on one of the dynamic disks where you want to create the striped volume and select New Volume from the menu that appears.
  3. Using the New Volume Wizard, click Next, select Striped, and follow the instructions and answer the questions asked by the wizard.

Here are some guidelines about striped volumes:

  • You need at least two physical dynamic disks to create a striped volume.
  • You can create a striped volume onto a maximum of 32 disks.
  • Striped volumes are not fault tolerant.
  • For increased volume capacity, select disks that contain similar amounts of available disk space. A striped volume’s capacity is limited to the space available on the disk with the smallest amount of available space.
  • Whenever possible, use disks that are the same model and from the same manufacturer.
  • Striped volumes cannot be extended or mirrored. If you need to make a striped volume larger by adding another disk, you first have to delete the volume and then re-create it.

Mirrored Volumes and RAID-5 Volumes

You can create mirrored volumes and RAID-5 volumes only on dynamic disks running on Windows Server 2008, Windows Server 2003, or Windows 2000 Server computers. Both mirrored volumes and RAID-5 volumes are considered fault tolerant because these configurations can handle a single disk failure and still function normally. Mirrored volumes and RAID-5 volumes both require that an equal amount of disk space be available on each disk that will be a part of these volumes. A mirrored volume must use two physical disks—no more and no fewer than two physical hard disk drives. A RAID-5 volume must use at least three physical hard disks up to a maximum of 32 physical disks.

Many network administrators and consultants agree that hardware-based fault-tolerant solutions are more robust and reliable than software-based fault-tolerant configurations. By installing one or more RAID controller adapter cards into a server, you can set up several different types of hardware fault tolerance, such as mirroring, RAID-5, RAID 10 (mirrored volumes that are part of a striped array set), and RAID 0+1 (striped volumes that are part of a mirrored set). When you use hardware RAID, you can retain basic disks or you can convert disks to dynamic; hardware RAID is hidden to Windows Server 2008. Of course, it’s less expensive to implement a software solution, such as setting up mirrored volumes or RAID-5 volumes using the Disk Management console in Windows Server 2008, but often the improved performance, reliability, and flexibility of hardware-based RAID far outweighs its extra cost.

Working with Mirrored Volumes

A mirrored volume uses volumes stored on two separate physical disks to “mirror” (write) the data onto both disks simultaneously and redundantly. This configuration is also referred to as RAID-1. If one of the disks in the mirrored configuration fails, Windows Server 2008 writes an event into the system log of the Event Viewer. The system functions normally (unless the second disk fails) until the failed disk is replaced and then the volume can be mirrored again. Mirrored volumes cost you 50% of your available storage space because of the built-in redundancy. If you mirror two 70GB disks, you are left with just 70GB of space rather than 140GB.

You can make mirrored volumes more robust by installing a separate hard disk controller for each disk; technically, this is known as disk duplexing. Disk duplexing is better than disk mirroring because you alleviate the single point of failure by having one controller for each disk. Under Windows Server 2008, disk duplexing is still referred to as disk mirroring. You can create mirrored volumes only by using dynamic disks. To create a new empty mirrored volume from unallocated space, follow these steps:

  1. Open Disk Management.
  2. Right-click an area of unallocated space on a dynamic disk and select New Volume.
  3. Click Next for the New Volume Wizard welcome window.
  4. Click Mirrored as the volume type option and click Next.
  5. Select one of the available dynamic disks and click Add.
  6. Enter the amount of storage space to be used (in MB) for this mirrored volume, up to the maximum available space on the first disk that you selected, and then click Next.
  7. Assign the new volume a drive letter, mount the volume in an empty NTFS folder, or choose not to assign the volume a drive letter or path and click Next.
  8. Choose whether to format the new mirrored volume. If you choose to format the new volume, specify the following settings:
    • File system (NTFS is the only option for dynamic volumes under the Disk Management console)
    • Allocation unit size
    • Volume label
    • Mark the check box to Perform a Quick Format (if desired)
    • Mark the check box to Enable File and Folder Compression (if desired)
  9. Click Next to continue.
  10. Click Finish to complete the New Volume Wizard.

To create a mirrored volume from a boot or system volume, or to create a mirrored volume from an existing volume that already contains data, follow these steps:

  1. Open Disk Management.
  2. Right-click an existing dynamic volume and select Add Mirror.
  3. Select one of the available dynamic disks on which to create the redundant volume and click Add Mirror.

You should be aware of some important issues and guidelines before you attempt to mirror system or boot volumes:

  • When you mirror volumes stored on ATA disks, you must change the jumper switch on the nonfailed drive to the master position (on restart) if the master disk on the primary IDE channel fails, until you replace the failed disk.
  • Microsoft does not recommend mirroring the system volume using one ATA disk and one SCSI disk because the system can encounter startup problems if one of the drives fails.
  • If you plan to use separate SCSI controllers for each SCSI disk that you will mirror, you should use identical controllers from the same manufacturer.
  • For a mirrored system volume, be sure to run a test to simulate a disk failure and attempt to start the system from the remaining mirrored volume. Perform this test regularly as part of your backup routine before a real failure occurs.

You can stop mirroring a volume by either breaking or removing the mirror. When you break a mirrored volume, each volume that makes up the mirror becomes an independent simple volume, and they are no longer fault tolerant. When you remove a mirrored volume, the removed mirrored volume becomes unallocated space on its disk, whereas the remaining mirrored volume becomes a simple volume that is no longer fault tolerant. All data that was stored on the removed mirrored volume is erased. To break a mirrored volume, take these steps:

  1. Open Disk Management.
  2. Right-click one of the mirrored volumes that you want to break and select Break Mirrored Volume.
  3. Click Yes in the Break Mirrored Volume message box.

If you want to completely destroy one of the mirrored volumes and leave just one of the volumes intact, you need to perform a removal procedure instead of simply breaking the mirrored volumes. Take these steps to remove a mirrored volume:

  1. Open Disk Management.
  2. Right-click a mirrored volume and then select Remove Mirror.
  3. At the Remove Mirror dialog box, select the disk from which you want to completely erase the mirrored volume and turn the volume into unallocated space. The remaining volume stays with all its data intact as a simple volume.
  4. Click the Remove Mirror button.
  5. Click Yes to confirm the removal action at the Disk Management message box that appears.

Working with RAID-5 Volumes

Windows Server 2008 supports disk striping with parity (RAID-5) volumes with the Disk Management console and through the diskpart.exe command-line utility. You need a minimum of three physical disks to create a RAID-5 volume. You are limited to a maximum of 32 physical disks in creating a RAID-5 volume under Windows Server 2008. In creating a fault-tolerant volume using a RAID-5 configuration, you effectively lose an amount of storage equivalent to the capacity of one of the disks because parity information gets stored across all the disks (disk striping with parity). For example, if you use three 70GB disks, your RAID-5 volume can store up to approximately 140GB of data. The remaining 70GB is used for storing the important parity data across all three disks in case of a failure—a 33% loss of available storage capacity. However, as you add disks to a RAID-5 volume, the percentage of lost storage space diminishes. For example, if you use five 70GB disks, you would again lose 70GB of available storage capacity, but that accounts only for a 20% overall loss in capacity (70GB divided by 350GB total available disk space equals .20, or 20%). In the event that one disk within the RAID-5 volume fails, the remaining disks can re-create the data stored on the failed disk as soon as a new disk is installed to replace the failed disk. To create a RAID-5 volume using Disk Management, follow these steps:

  1. Open Disk Management. Be sure that the computer has three or more dynamic disks—each with unallocated space.
  2. Right-click an area of unallocated space on one of the dynamic disks that you want to use for the RAID-5 volume and select New Volume.
  3. Click Next for the Welcome to the New Volume Wizard window.
  4. Select the RAID-5 option button and click Next.
  5. Select each available disk that you want to use as part of the RAID-5 volume from within the Available list box and click Add for each one. You must select at least 3 disks and no more than 32 disks.
  6. Select any disks that you do not want to use as part of the RAID-5 volume within the Selected list box, and click Remove to remove any disks that you do not want to include as a part of the RAID-5 volume.
  7. Enter the storage capacity that you want for the RAID-5 volume in the Select the Amount of Space in MB spin box and click Next to continue.
  8. Choose to assign the volume a drive letter, mount the volume in an empty NTFS folder, or choose to not assign a drive letter or path to the new RAID-5 volume and click Next.
  9. Choose whether to format the new RAID-5 volume. If you choose to format the new volume, specify the following settings:
    • File system (NTFS is the only option for dynamic volumes under the Disk Management console).
    • Allocation unit size.
    • Volume label.
    • Mark the check box to Perform a Quick Format (if desired).
    • Mark the check box to Enable File and Folder Compression (if desired).
  10. Click Next to continue.
  11. Click Finish to complete the New Volume Wizard.

If one disk within a RAID-5 volume is intermittently failing, you can attempt to reactivate it by right-clicking the disk and selecting Reactivate Disk. If one disk within a RAID-5 volume appears to be permanently failed, you can replace that failed disk with another dynamic disk attached to the computer or you can install a new disk. To regenerate the RAID-5 volume, right-click the RAID-5 volume on the failed disk and select Repair Volume. The replacement disk must contain at least as much unallocated space as that used by the failed disk for the RAID-5 volume.

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