Repairing a striped set without parity
A striped set without parity doesn’t have fault tolerance. If a drive that’s part of a striped set fails, the entire striped set is unusable. Before you try to restore the striped set, you should repair or replace the failed drive. Then you need to re-create the striped set and recover the data contained on the striped set from backup.
Regenerating a striped set with parity
With RAID-5, you can recover the striped set with parity if a single drive fails. You’ll know that a striped set with parity drive has failed because the set’s status changes to Failed Redundancy and the individual volume’s status changes to Missing, Offline, or Online (Errors).
You can repair RAID-5 disks, but you must rebuild the set by using disks with the same partition style-either MBR or GPT. You need to get all drives in the RAID-5 set online. The set’s status should read Failed Redundancy. The corrective action you take depends on the failed volume’s status:
■ If the status is Missing or Offline, make sure the drive has power and is connected properly. Then start Disk Management, press and hold or right-click the failed volume, and select Reactivate Volume. The drive’s status should change to Regenerating and then to Healthy. If the drive’s status doesn’t return to Healthy, press and hold or right-click the volume and select Regenerate Parity.
■ If the status is Online (Errors), press and hold or right-click the failed volume, and select Reactivate Volume. The drive’s status should change to Regenerating and then to Healthy. If the drive’s status doesn’t return to Healthy, press and hold or right-click the volume and select Regenerate Parity.
■ If one of the drives shows as Unreadable, you might need to rescan the drives on the system by choosing Rescan Disks from Disk Management’s Action menu. If the drive status doesn’t change, you might 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. Press and hold or 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 the RAID-5 set is already using. If you don’t have enough space, the Repair Volume command is unavailable, and you need to free space by deleting other volumes or by replacing the failed drive.
BEST PRACTICES If possible, you should back up the data before you perform this procedure to ensure that if you have problems, you can recover your data.
Standards-based storage management
Standards-based storage management focuses on the storage volumes themselves rather than the underlying physical layout, relying on hardware to handle the architecture particulars for data redundancy and the portions of disks that are presented as usable disks. This means the layout of the physical disks is controlled by the storage subsystem instead of by the operating system.
Getting started with standards-based storage
With standards-based management, the physical layout of disks (spindles) is abstracted, so a “disk” can be a logical reference to a portion of a storage subsystem (a virtual disk) or an actual physical disk. This means a disk simply becomes a unit of storage and volumes can be created to allocate space within disks for file systems.
Taking this concept a few steps further, you can pool available space on disks so that units of storage (virtual disks) can be allocated from this pool on an as-needed basis. These units of storage, in turn, are apportioned with volumes to allocate space and create usable file systems.
Technically, the pooled storage is referred to as a storage pool and the virtual disks created within the pool are referred to as storages spaces. Given a set of “disks,” you can create a single storage pool by allocating all the disks to the pool or create multiple storage pools by allocating disks separately to each pool.
REAL WORLD Trust me when I say this all sounds more complicated than it is. When you throw storage subsystems into the mix, it’s really a three-layered architecture. In Layer 1, the layout of the physical disks is controlled by the storage subsystem. The storage system likely will use some form of RAID to ensure that data is redundant and recoverable in case of failure. In Layer 2, the virtual disks created by the arrays are made available to servers. The servers simply see the disks as storage that can be allocated. Windows Server can apply software-level RAID or other redundancy approaches to help protect against failure. In Layer 3, the server creates volumes on the virtual disks, and these volumes provide the usable file systems for file and data storage.
Working with standards-based storage
When you are working with File And Storage Services, you can group available physical disks into storage pools so that you can create virtual disks from available capacity. Each virtual disk you create is a storage space. Storage Spaces are made available through the Storage Services role service, which is automatically installed on every server running Windows Server 2012 R2.
To integrate Storage Spaces with standards-based storage management frameworks, you’ll want to add the Windows Standards-Based Storage Management feature to your file servers. When a server is configured with the File Services And Storage role, the Windows Standards-Based Storage Management feature adds components and updates Server Manager with the options for working with standards-based volumes. You might also want to do the following:
■ Add the Data Deduplication role service if you want to enable data deduplication.
■ Add the iSCSI Target Server and iSCSI Target Storage Provider role services if you want the server to host iSCSI virtual disks.
After you configure your servers as appropriate for your environment, you can select the File And Storage Services node in Server Manager to work with your storage volumes, and additional options will be available as well. The Servers subnode lists file servers that have been configured for standards-based management.
As Figure 2–5 shows, the Volumes subnode lists allocated storage on each server according to how volumes are provisioned and how much free space is available.
Volumes are listed regardless of whether the underlying disks are physical or virtual. Press and hold or right-click a volume to display management options, including the following:
■ Configure Data Deduplication Allows you to enable and configure data deduplication for NTFS volumes. If the feature is enabled, you can then also use this option to disable data deduplication.
■ Delete Volume Allows you to delete the volume. The space that was used is then marked as unallocated on the related disk.
■ Extend Volume Allows you to extend the volume to unallocated space of the related disk.
■ Format Allows you to create a new file system on the volume that overwrites the existing volume.
■ Manage Drive Letter And Access Paths Allows you to change the drive letter or access path associated with the volume.
■ New iSCSI Virtual Disk Allows you to create a new iSCSI virtual disk that is stored on the volume.