Administering Volume Sets and RAID Arrays
from Chapter 11, Microsoft Windows 2000 Administrator's Pocket Consultant by William R. Stanek.
When you work with Microsoft Windows 2000 servers, you'll often need to perform advanced disk setup procedures, such as creating a volume set or setting up a RAID array. The following are some of the tasks that you can perform with Disk Manager.
With a volume set, you can create a single volume that spans multiple drives. Users can access this volume as if it were a single drive, regardless of how many drives the actual volume is spread over. A volume that is on a single drive is referred to as a simple volume. A volume that spans multiple drives is referred to as a spanned volume.
With RAID arrays, you can protect important business data and, sometimes, improve the performance of drives. RAID is an acronym for redundant array of independent disks. Windows 2000 supports three different levels of RAID: 0, 1, and 5. You implement RAID arrays as mirrored, striped, and striped with parity volumes.
In Windows 2000, volumes are designed to be used with dynamic disks. If you created volumes under Microsoft Windows NT 4.0, you'll need to upgrade the basic drives containing the volumes to dynamic drives and then manage the volumes as you would any other Windows 2000 volume. If you don't do this, your management options for the volumes are limited.
Volume sets and RAID arrays are created on dynamic drives and are only accessible to Windows 2000 and later. Because of this, if you dual boot a computer to a previous version of Windows, the dynamic drives are unavailable. However, computers running previous versions of Windows can access the drives over the network—just like any other network drive.
Using Volumes and Volume Sets
You create and manage volumes in much the same way as partitions. A volume is a drive section that can be used to store data directly.
Note: With spanned and striped volumes on basic disks, you can delete the volume but you can't create or extend volumes. With mirrored volumes on basic disks, you can delete, repair, and resync the mirror. You can also break the mirror. With striped with parity volumes (RAID 5) on basic disks, you can delete or repair the volume but you can't create new volumes.
As Figure 11-1 shows, Disk Management color codes volumes by type, much like partitions. Volumes also have a specific
Layout Volume layouts include simple, spanned, mirrored, striped, and striped with parity.
Type Volumes always have the type dynamic.
File system As with partitions, each volume can have a different file system type, such as FAT (file allocation table), FAT 32, or NTFS (Windows NT file system).
Figure 11-1: Disk Management displays volumes much like partitions.
Status The state of the drive. For details on drive state, see the section of Chapter 10 entitled "Understanding Drive Status."
Capacity The total storage size of the drive.
An important advantage of dynamic volumes over basic volumes is your ability to make changes to volumes and drives without having to restart the system (in most cases). Volumes also let you take advantage of the fault tolerance enhancements of Windows 2000. While you can't use dynamic drives with previous versions of Windows, you can install other operating systems and dual boot a Windows 2000 system. To do this, you must create a separate volume for the other operating system. For example, you could install Windows 2000 on volume C and Linux on volume D.
With volumes, you can
Assign drive letters, as discussed in the section of Chapter 10 entitled "Assigning Drive Letters."
Assign drive paths, as discussed in the section of Chapter 10 entitled "Assigning Drive Paths."
Create any number of volumes on a disk as long as you have free space.
Create volumes that span two or more disks and, if necessary, configure fault tolerance.
Extend volumes to increase the capacity of the volume.
Designate Active, System, and Boot volumes, as described in the section of Chapter 10 entitled "Special Considerations for Basic and Dynamic Disks."
Understanding Volume Sets
With volume sets, you can create volumes that span several drives. To do this, you use free space on different drives to create what users see as a single volume. Files are stored on the volume set segment by segment, with the first segment of free space being used first to store files. When this segment fills up, the second segment is used, and so on.
You can create a volume set using free space on up to 32 hard disk drives. The key advantage to volume sets is that they let you tap into unused free space and create a usable file system. The key disadvantage is that if any hard disk drive in the volume set fails, the volume set can no longer be used—which means that essentially all the data on the volume set is lost.
Creating Volumes and Volume Sets
You create volumes and volume sets by completing the following steps:
In the Disk Management Graphical view, right-click an area marked Unallocated on a dynamic disk and then choose Create Volume. This starts the Create Volume Wizard. Read the welcome dialog box, and then click Next.
As shown in Figure 11-2, select Simple Volume to create a volume on a single disk or Spanned Volume to create a volume set on multiple disks. Simple volumes can be formatted as FAT, FAT 32, or NTFS. To make management easier, you should format volumes that span multiple disks as NTFS. NTFS formatting allows you to expand the volume set, if necessary.
Note: If you find that you need more space on a volume, you can extend simple and spanned volumes. You do this by selecting an area of free space and adding it to the volume. You can extend a simple volume within the same disk. You can also extend a simple volume onto other disks. When you do this, you create a spanned volume, which must be formatted as NTFS.
You should see the Select Disks dialog box shown in Figure 11-3. Use this dialog box to select dynamic disks that are a part of the volume and to size the volume segments on those disks.
Available dynamic disks are shown in the All Available Dynamic Disks list box. Select a disk in this list box, and then click Add >> to add the disk to the Selected Dynamic Disks list box. If you make a mistake, you can remove disks from the Selected Dynamic Disks list box by selecting the disk and then clicking <<Remove.
Select a disk in the Selected Dynamic Disks list box, and then use the For Selected Disk … MB combo box to specify the size of the volume on the selected disk. The Maximum field shows you the largest area of free space available on the selected disk. The Total Volume Size field shows you the total disk space selected for use with the volume.
Figure 11-2: Select a volume type, and then click Next.
Figure 11-3: Use the Select Disks dialog box to select disks to be a part of the volume, and then size the volume on each disk.
Tip Although you can size the volume set any way you want, you may want to take a moment to consider how you'll use volume sets on the current workstation or server. Simple and spanned volumes aren't fault tolerant. Rather than creating one monstrous volume with all the available free space, you may want to create several smaller volumes.
Specify whether you want to assign a drive letter or path. These options are used as follows:
Assign A Drive Letter To assign a drive letter, choose this option and then select an available drive letter in the selection list provided.
Mount This Volume To An Empty Folder That Supports Drive Paths To assign a drive path, choose this option and then type the path to an existing folder or click Browse to search for or create a folder.
Do Not Assign A Drive Letter Or Drive Path To create the volume without assigning a drive letter or path, choose this option. You can assign a drive letter or path later, if necessary.
As shown in Figure 11-4, determine whether the volume should be formatted. If you elect to format the volume, follow the steps described in the section of Chapter 10 entitled "Formatting Partitions."
Figure 11-4: Format a volume by specifying its file system type and volume label.
Click Next, and then click Finish. If you add volumes to a physical drive that contains the Windows 2000 operating system, you may inadvertently change the number of the boot volume. Read the warning prompts and then make any necessary changes to the BOOT.INI file as described in Chapter 10 under "Updating the Boot Disk."
Deleting Volumes and Volume Sets
You use the same technique to delete all volumes, whether they're simple, spanned, mirrored, striped, or striped with parity. Deleting a volume set removes the associated file system and data. So before you delete a volume set you should back up any files and directories that the volume set contains.
To delete volumes, follow these steps:
In Disk Management, right-click any volume in the set and then choose Delete Volume. You can't delete a portion of a spanned volume without deleting the entire volume.
Confirm that you want to delete the volume by clicking Yes.
If you delete a volume on a physical drive that contains the Windows 2000 operating system, the number of the boot partition may change. If so, you'll need to update the BOOT.INI file as described in the section of Chapter 10 entitled "Updating the Boot Disk."
Extending a Simple or Spanned Volume
Windows 2000 provides several ways to extend NTFS volumes that aren't part of a mirror set or a stripe set. You can extend a simple volume and you can extend existing volume sets. When you extend volumes, you add free space to them.
Note: When extending volume sets, there are many things you can't do. You can't extend boot or system volumes. You can't extend volumes that use mirroring or striping. You can't extend a volume onto more than 32 disks, either. Additionally, you can't extend FAT or FAT 32 volumes—you must first convert them to NTFS. And you can't extend simple or spanned volumes that were upgraded from basic disks. As you work with volume sets, please keep these exceptions in mind.
To extend an NTFS volume, complete the following steps:
In Disk Management, right-click the simple or spanned volume that you want to extend, and then select Extend Volume. This starts the Extend Volume Wizard. Read the welcome dialog box, and then click Next.
You can now select dynamic disks that are a part of the volume, and size the volume segments on those disks as described in steps 5–7 of the "Creating Volumes and Volume Sets" section of this chapter.
Note: A volume set that spans multiple drives can't be mirrored or striped. Only simple volumes can be mirrored or striped.
Click Next and then click Finish.
You manage volumes much like you manage partitions. You can
Assign drive letters and paths
Change or delete volume labels
Convert a volume to NTFS
Check a drive for errors and bad sectors
Compress drives and data
Encrypt drives and data
Follow the techniques outlined in the section of Chapter 10 entitled "Managing Existing Partitions and Drives."
Improved Performance and Fault Tolerance with RAIDs
You'll often want to give important data increased protection from drive failures. To do this, you can use RAID technology to add fault tolerance to your file systems. With RAID 1 you increase data integrity and availability by creating copies of the data. With RAID 5, you increase data integrity by creating a volume with data and parity striped intermittently across three or more physical disks. You can also use RAID to improve the performance of your disks. However, the data integrity feature is not available with RAID 0.
Different implementations of RAID technology are available. These implementations are described in terms of levels. Currently, the most widely implemented RAID levels are 0, 1, 2, 3, 4, 5, 6, 7, 10, and 53. Each RAID level offers different features. Windows 2000 supports RAID levels 0, 1, and 5.
Use RAID 0 to improve the performance of your drives. You can also use RAID 0 to gain more space by combining leftover sections on two or more physical drives.
Use RAID 1 and 5 to provide fault tolerance for data.
Table 11-1 provides a brief overview of the supported RAID levels. This support is completely software-based and is only available on Windows 2000 servers.
Table 11-1 Windows 2000 Server Support for RAID
Two or more volumes, each on a separate drive, are configured as a stripe set. Data is broken into blocks, called stripes, and then written sequentially to all drives in the stripe set.
Two volumes on two drives are configured identically. Data is written to both drives. If one drive fails, there's no data loss because the other drive contains the data. (Doesn't include disk striping.)
Redundancy. Better write performance than disk striping with parity.
Disk striping with parity
Uses three or more volumes, each on a separate drive, to create a stripe set with parity error checking. In the case of failure, data can be recovered.
Fault tolerance with less overhead than mirroring. Better read performance than disk mirroring.
The most common RAID levels in use on Windows 2000 servers are level 1 disk mirroring and level 5 disk striping with parity. Disk mirroring is the least expensive way to increase data protection with redundancy. Here you use two identically sized volumes on two different drives to create a redundant data set. If one of the drives fails, you can still obtain the data from the other drive.
On the other hand, disk striping with parity requires more disks—a minimum of three—but offers fault tolerance with less overhead than disk mirroring. If any of the drives fail, the data can automatically be recovered by combining blocks of data on the remaining disks with a parity record. Parity is a method of error checking that uses a special algorithm to create a value that could be used to recover lost data. You use this parity sector to recover data in case of hard drive failure.
from Microsoft Windows 2000 Administrator's Pocket Consultant by William R. Stanek. Copyright © 1999 Microsoft Corporation.