Chapter 11 - Administering Volume Sets and RAID Arrays

Article
12/09/2009

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.

Volume Basics

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.

Managing Volumes

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
Defragment disks
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

RAID Level	RAID Type	Description	Major Advantages
0	Disk striping	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.	Speed/Performance
1	Disk mirroring	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.
5	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.

Implementing RAID on Windows 2000 Servers

For server systems, Windows 2000 supports disk mirroring, disk striping, and disk striping with parity. How to implement these RAID techniques is discussed in the sections that follow.

Note: Some operating systems, such as MS-DOS, don't support RAID. If you dual boot your system to one of these noncompliant operating systems, your RAID-configured drives will be unusable.

Implementing RAID 0: Disk Striping

RAID level 0 is disk striping. With disk striping, two or more volumes—each on a separate drive—are configured as a stripe set. Data written to the stripe set is broken into blocks that are called stripes. These stripes are written sequentially to all drives in the stripe set. You can place volumes for a stripe set on up to 32 drives, but in most circumstances sets with two to five volumes offer the best performance improvements over non-RAID volumes because data from multiple drives is simultaneously accessed. Beyond this, the performance improvement decreases significantly.

The major advantage of disk striping is speed. Data can be accessed on multiple disks using multiple drive heads, which improves performance considerably. However, this performance boost comes with a price tag. As with volume sets, if any hard disk drive in the stripe set fails, the stripe set can no longer be used, which means that essentially all data in the stripe set is lost. You'll need to recreate the stripe set and restore the data from backups. Data backup and recovery are discussed in Chapter 14.

Note: The boot and system volumes can't be part of a striped set. Don't use disk striping with these volumes.

When you create stripe sets, you'll want to use volumes that are approximately the same size. Disk Management bases the overall size of the stripe set on the smallest volume size. Specifically, the maximum size of the stripe set is a multiple of the smallest volume size. For example, if you have three physical drives and if the smallest volume is 50 MB, the maximum size for the stripe set is 150 MB.

To maximize performance of the stripe set, there are several things you can do:

Use disks that are on separate disk controllers. This allows the system to simultaneously access the drives.
Don't use the disks containing the stripe set for other purposes. This allows each disk to dedicate its time to the stripe set.

You create a stripe set 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.
Select Striped Volume as the volume type. Create the volume as described previously in this chapter in the section entitled "Creating Volumes and Volume Sets." The key difference is that you need at least two dynamic disks to create a striped volume.
Once you create a striped volume, you can use the volume just like any other volume. You can't expand a stripe set once it's created. Because of this, you should carefully consider the setup before you implement it.

Implementing RAID 1: Disk Mirroring

RAID level 1 is disk mirroring. With disk mirroring, you use identically sized volumes on two different drives to create a redundant data set. Here, the drives are written with identical sets of information, and if one of the drives fails, you can still obtain the data from the other drive.

Disk mirroring offers about the same fault tolerance as disk striping with parity. Because mirrored disks don't need to write parity information, they can offer better write performance in most circumstances. However, disk striping with parity usually offers better read performance because read operations are spread over multiple drives.

The major drawback to disk mirroring is that it effectively cuts the amount of storage space in half. For example, to mirror a 5 GB drive, you need another 5 GB drive. That means you use 10 GB of space to store 5 GB of information.

Note: Unlike with disk striping, with disk mirroring you can mirror any volume. This means you can mirror the boot and system volumes if you want.

As with disk striping, you'll often want the mirrored disks to be on separate disk controllers. This provides increased protection against failure of the disk controller. If one of the disk controllers fails, the disk on other controller is still available. Technically, when you use two separate disk controllers to duplicate data, you're using a technique known as disk duplexing. Figure 11-5 shows the difference between the two techniques. Disk mirroring typically uses a single drive controller, but disk duplexing uses two drive controllers.

If one of the mirrored drives in a set fails, disk operations can continue. Here, when users read and write data, the data is written to the remaining disk. You'll need to break the mirror before you can fix the mirror. To learn how, see the section of this chapter entitled "Managing RAIDs and Recovering from Failures."

Creating a Mirror Set in Disk Management

You create a mirror set 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.
Select Mirrored Volume as the volume type. Create the volume as described previously in the section of this chapter entitled "Creating Volumes and Volume Sets." The key difference is that you must create two identically sized volumes and these volumes must be on separate dynamic drives.

Figure 11-5: While disk mirroring typically uses a single drive controller to create a redundant data set, disk duplexing uses two drive controllers. Otherwise, the techniques are essentially the same.
As with other RAID techniques, mirroring is transparent to users. Users see the mirrored set as a single drive that they can access and use like any other drive.

Note: The status of a normal mirror is Healthy. During the creation of a mirror, you may see a status of Initializing. This tells you that Disk Management is setting up the mirror.

Mirroring an Existing Volume

Rather than creating a new mirrored volume, you can use an existing volume to create a mirrored set. To do this, the volume you want to mirror must be a simple volume, and you must have an area of unallocated space on a second dynamic drive of equal or larger space than the existing volume.

In Disk Management, you mirror an existing volume by completing the following steps:

Right-click the simple volume you want to mirror, and then select Add Mirror. This starts the Add Mirror Wizard.
Use the wizard dialog boxes to select and configure the second volume in the mirrored set. The steps you follow are similar to those outlined in the "Creating Volumes and Volume Sets" section of this chapter.

Implementing RAID 5: Disk Striping with Parity

RAID level 5 is disk striping with parity. With this technique, you need a minimum of three hard disk drives to set up fault tolerance. The volumes on these drives are sized identically by Disk Management. Although you can place volumes for a stripe set on up to 32 drives, in most circumstances sets with two to five volumes offer the best performance improvements. Beyond this, the performance improvement decreases significantly.

RAID 5 is essentially an enhanced version of RAID 1—with the key addition of fault tolerance. Fault tolerance ensures that the failure of a single drive won't bring down the entire drive set. Instead, the set continues to function with disk operations directed at the remaining volumes in the set.

To allow for fault tolerance, RAID 5 writes parity checksums with the blocks of data. If any of the drives in the stripe set fails, you can use the parity information to recover the data. (This process, called regenerating the striped set, is covered in the section of this chapter entitled "Managing RAIDs and Recovering from Failures.") If two disks fail, however, the parity information isn't sufficient to recover the data, and you'll need to rebuild the striped set from backup.

Note: The boot and system volumes can't be part of a striped set. Don't use disk striping with parity on these volumes.

Creating a Stripe Set with Parity in Disk Management

In Disk Management, you can create a stripe set with parity 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.
Select RAID-5 Volume as the volume type. Create the volume as described previously in the section of this chapter entitled "Creating Volumes and Volume Sets." The key difference is that you need to select free space on three separate dynamic drives.
Once you create a stripe set, users can use the set just like they would a normal drive. Keep in mind that you can't expand a stripe set once it's created by adding more disks or replacing one of the disks with a larger drive. Because of this, you should carefully consider the setup before you implement it.

Managing RAIDs and Recovering from Failures

Managing mirrored drives and stripe sets is somewhat different from managing other drive volumes, especially when it comes to recovering from failure. The techniques you'll need to manage RAID arrays and to recover from failure are covered in this section.

Breaking a Mirrored Set

You may want to break a mirror for two reasons:

If one of the mirrored drives in a set fails, disk operations can continue. Here, when users read and write data, these operations use the remaining disk. Still, at some point you'll need to fix the mirror, and to do this you must first break the mirror and then reestablish it.
If you no longer want to mirror your drives, you may also want to break a mirror. This allows you to use the disk space for other purposes.

Note: Although breaking a mirror doesn't delete the data in the set, you should always back up the data before you perform this procedure. This ensures that if you have problems, you can recover your data.

In Disk Management, you can break a mirrored set by following these steps:

Right-click one of the volumes in the mirrored set, and then choose Break Mirror.
Confirm that you want to break the mirror by clicking Yes. This creates two independent volumes.

Resynchronizing and Repairing a Mirrored Set

Windows 2000 automatically synchronizes mirrored volumes on dynamic drives. However, data on mirrored drives can get out of sync. For example, if one of the drives goes offline, data is only written to the drive that's online.

You can resynchronize and repair mirrored sets on basic and dynamic disks, but you must rebuild the set using the same disk type. To resynchronize a failed mirror set, complete the following steps:

You need to get both drives in the mirrored set online. The status of the mirrored set should read Failed Redundancy. The corrective action you take depends on the status of the failed volume.
If the status is Missing or Offline, make sure that the drive has power and is connected properly. Afterward, start Disk Management, right-click the failed volume and select Reactivate Disk. The drive's status should change to Regenerating and then to Healthy. If the volume doesn't return to the Healthy status, right-click the volume and then click Resynchronize Mirror.
If the status is Online (Errors), right-click the failed volume and select Reactivate Disk. The drive's status should change to Regenerating and then to Healthy. If the volume doesn't return to the Healthy status, right-click the volume and then click Resynchronize Mirror.
If one of the drives shows as Unreadable, you may need to rescan the drives on the system by selecting Rescan Disks from Disk Management's Action menu. If the drive status doesn't change, you may need to reboot the computer.
If one of the drives still won't come back online, right-click the failed volume and then select Remove Mirror. Next, right-click the remaining volume in the original mirror and then select Add Mirror. You'll now need to mirror the volume on an unallocated area of free space. If you don't have free space, you'll need to create space by deleting other volumes or replacing the failed drive.

Repairing a Mirrored System Volume to Enable Boot

The failure of a mirrored drive may prevent your system from booting. Typically, this happens when you're mirroring the system or boot volume, or both, and the primary mirror drive has failed. To correct this problem, you need to replace the failed drive and then use an emergency boot disk for the system or a similarly configured system to enable system boot. This should not be confused with the emergency repair disk, which is mainly used to fix registry corruption. Creating an emergency boot disk is covered in Chapter 14.

Editing BOOT.INI for the Mirror

Once you have an emergency boot disk, you need to edit the BOOT.INI file it contains so that the operating system loads from the secondary mirror. This file contains entries that look like this:

[boot loader] timeout=30 default=multi(0)disk(0)rdisk(0)volume(2)\WIN2000[operating
systems]multi(0)disk(0)rdisk(0)volume(2)\WIN2000="Windows 2000Server"

If the secondary mirror drive was on drive 2, you could update the BOOT.INI file shown earlier as follows:

[boot loader] timeout=30 default=multi(0)disk(0)rdisk(1)volume(2)\WIN2000[operating
systems]multi(0)disk(0)rdisk(1)volume(2)\WIN2000=""Windows 2000Server"

Note: For a more detailed explanation of BOOT.INI, see the section of Chapter 10 entitled "Updating the Boot Disk."

Booting and Rebooting the System

Once you update the BOOT.INI file, you can use the emergency boot disk to boot your system. When the system boots, you'll need to complete the following steps:

Break the mirror set and then re-create the mirror on the drive you replaced, which is usually drive 0. Right-click the remaining volume that was part of the original mirror and then select Add Mirror. Next, follow the technique described in the "Mirroring an Existing Volume" section of this chapter.
When the mirror is completely rebuilt, use Disk Management to break the mirror again. Make sure that the primary drive in the original mirror set has the drive letter that was previously assigned to the complete mirror. If it doesn't, assign the appropriate drive letter.
Right-click the original system volume, and then select Add Mirror. Now re-create the mirror.
Update BOOT.INI so that the original system volume is used during startup.

Removing a Mirrored Set

In Disk Management, you can remove one of the volumes from a mirrored set. When you do this, all data on the removed mirror is deleted and the space it used is marked as Unallocated.

To remove a mirror, complete the following steps:

In Disk Management, right-click one of the volumes in the mirrored set and then choose Remove Mirror.
Confirm the action when prompted. All data on the removed mirror is deleted.

Repairing a Stripe Set Without Parity

A stripe set without parity doesn't have fault tolerance. If a drive that is part of a stripe set fails, the entire stripe set is unusable. Before you try to restore the stripe set, you should repair or replace the failed drive. Afterward, you need to re-create the stripe set and then recover the data contained on the stripe set from backup.

Regenerating a Stripe Set with Parity

With RAID 5 you can recover the stripe set if a single drive fails. You'll know that a stripe set with parity drive has failed because the status of the set changes to Failed Redundancy and the status of the individual volume changes to Missing, Offline, or Online (Errors).

You can repair RAID 5 on basic and dynamic disks, but you must rebuild the set using the same disk type. To resolve problems with the RAID 5 set, complete the following steps:

You need to get all drives in the RAID 5 set online. The status of the set should read Failed Redundancy. The corrective action you take depends on the status of the failed volume.

Note: If possible, you should back up the data before you perform this procedure. This ensures that if you have problems, you can recover your data.
If the status is Missing or Offline, make sure that the drive has power and is connected properly. Afterward, start Disk Management, right-click the failed volume, and select Reactivate Disk. The drive's status should change to Regenerating and then to Healthy. If the status of the drive doesn't return to Healthy, right-click the volume and select Regenerate Parity.
If the status is Online (Errors), right-click the failed volume and select Reactivate Disk. The drive's status should change to Regenerating and then to Healthy. If the status of the drive doesn't return to Healthy, right-click the volume and select Regenerate Parity.
If one of the drives shows as Unreadable, you may need to rescan the drives on the system by selecting Rescan Disks from Disk Management's Action menu. If the drive status doesn't change, you may need to reboot the computer.
If one of the drives still won't come back online, you need to repair the failed region of the RAID 5 set. Right-click the failed volume and then select Remove Volume. You now need to select an unallocated space on a separate dynamic disk for the RAID 5 set. This space must be at least as large as the region to repair, and it can't be on a drive that's already being used by the RAID 5 set. If you don't have enough space, the Repair Volume command is unavailable, and you'll need to free space by deleting other volumes or replacing the failed drive.

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