REAL WORLD Standards-based approaches to storage management can also be used with a server’s internal disks. When internal disks are used in this way, however, the internal disks-such as virtual disks on attached storage-are resources to be allocated by using standards-based approaches. This means you can create virtual disk volumes on the physical disks, add the physical disks to storage pools, and create Internet SCSI (iSCSI) virtual disks that can be targeted. You can also enable data deduplication on your virtual disks. You can’t, however, use the operating system’s volume set or RAID array features, because standards-based, storage management approaches rely on the storage subsystem to manage the physical disk architecture.
Using volumes and volume sets
You create volume sets and RAID arrays on dynamic drives. 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 volume is spread over. A volume that’s 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 a RAID array, you can protect important business data and sometimes improve the performance of drives. RAID can be implemented by using the built-in features of the operating system (a software approach) or by using hardware. Windows Server 2012 R2 supports three levels of software RAID: 0, 1, and 5. RAID arrays are implemented as mirrored, striped, and striped with parity volumes.
You create and manage volumes in much the same way in which you create and manage partitions. A volume is a drive section you can use to store data directly.
NOTE With spanned and striped volumes on basic disks, you can delete a 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. For striped with parity volumes (RAID-5) on basic disks, you can delete or repair the volume, but you can’t create new volumes.
Understanding volume basics
Disk Management color codes volumes by type, much like it does partitions. As Figure 2–1 shows, volumes also have the following properties:
■ Layout Volume layouts include simple, spanned, mirrored, striped, and striped with parity.
■ Type Volumes always have the type dynamic . Partitions always have the type basic .
■ File System Like partitions, each volume can have a different file system type, such as FAT or NTFS file system. Note that FAT16 is available only when the partition or volume is 2 GB or less in size.
■ Status The state of the drive. In Graphical View, the state is shown as Healthy, Failed Redundancy, and so on. The next section, “Understanding volume sets,” discusses volume sets and the various states you might encounter.
■ Capacity The total storage size of the drive.
■ Free Space The total amount of available space on the volume.
■ % Free The percentage of free space out of the total storage size of the volume.
FIGURE 2–1 Disk Management displays volumes much like it does partitions.
An important advantage of dynamic volumes over basic volumes is that dynamic volumes enable you 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 Server 2012 R2. You can install other operating systems and dual boot a Windows Server 2012 R2 system by creating a separate volume for the other operating system. For example, you could install Windows Server 2012 R2 on volume C and Windows 8.1 on volume D.
With volumes, you can do the following:
■ Assign drive letters and drive paths as discussed in “Assigning drive letters and paths” later in this chapter
■ 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 volumes’ capacity
■ Designate active, system, and boot volumes as described in “Special considerations for basic and dynamic disks” in Chapter 1, “Managing file systems and drives”
Understanding volume sets
With volume sets, you can create volumes that span several drives by using free space on different drives to create what users perceive as a single volume. Files are stored on the volume set segment by segment, with the first segment of free space being used to store files before other segments. When the first 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.
Understanding the volume status is useful when you install new volumes or are trying to troubleshoot problems. Disk Management shows the drive status in Graphical View and Volume List view. Table 2–1 summarizes status values for dynamic volumes.
TABLE 2–1 Understanding and resolving volume status issues
| STATUS | DESCRIPTION | RESOLUTION |
|---|---|---|
| Data Incomplete | Spanned volumes on a foreign disk are incomplete. You must have forgotten to add the other disks from the spanned volume set. | Add the disks that contain the rest of the spanned volumes, and then import all the disks at one time. |
| Data Not Redundant | Fault-tolerant volumes on a foreign disk are incomplete. You must have forgotten to add the other disks from a mirror or RAID-5 set. | Add the remaining disks, and then import all the disks at one time. |
| Failed | An error disk status. The disk is inaccessible or damaged. | Ensure that the related dynamic disk is online. As necessary, press and hold or right-click the volume, and then tap or click Reactivate Volume. For a basic disk, you might need to check the disk for a faulty connection. |
| Failed Redundancy | An error disk status. One of the disks in a mirror or RAID-5 set is offline. | Ensure that the related dynamic disk is online. If necessary, reactivate the volume. Next, you might need to replace a failed mirror or repair a failed RAID-5 volume. |
| Formatting | A temporary status that indicates the volume is being formatted. | The progress of the formatting is indicated as the percent complete unless you choose the Perform A Quick Format option. |
| Healthy | The normal volume status. | The volume doesn’t have any known problems. You don’t need to take any corrective action. |
| Healthy (At Risk) | Windows had problems reading from or writing to the physical disk on which the dynamic volume is located. This status appears when Windows encounters errors. | Press and hold or right-click the volume, and then tap or click Reactivate Volume. If the disk continues to have this status or has this status periodically, the disk might be failing, and you should back up all data on the disk. |
| Healthy (Unknown Partition) | Windows does not recognize the partition. This can occur because the partition is from a different operating system or is a manufacturer-created partition used to store system files. | No corrective action is necessary. |
| Initializing | A temporary status that indicates the disk is being initialized. | The drive status should change after a few seconds. |
| Regenerating | A temporary status that indicates that data and parity for a RAID-5 volume are being regenerated. | Progress is indicated as the percent complete. The volume should return to Healthy status. |
| Resynching | A temporary status that indicates that a mirror set is being resynchronized. | Progress is indicated as the percent complete. The volume should return to Healthy status. |
| Stale Data | Data on foreign disks that are fault tolerant are out of sync. | Rescan the disks or restart the computer, and then check the status. A new status should be displayed, such as Failed Redundancy. |
| Unknown | The volume cannot be accessed. It might have a corrupted boot sector. | The volume might have a boot sector virus. Check it with an up-todate antivirus program. Rescan the disks or restart the computer, and then check the status. |