Книга: Windows Server 2012 R2 Storage, Security, & Networking Pocket Consultant

Creating a virtual disk in a storage space

Creating a virtual disk in a storage space

After you create a storage pool, you can allocate space from the pool to virtual disks that are available to your servers. Each physical disk allocated to the pool can be handled in one of three ways:

? As a data store that is available for use

? As a data store that can be manually allocated for use

? As a hot spare in case a disk in the pool fails or is removed from the subsystem

When a storage pool has a single disk, your only option for allocating space on that disk is to create virtual disks with a simple layout. A simple layout does not protect against disk failure. If a storage pool has multiple disks, you have these additional layout options:

? Mirror With a mirror layout, data is duplicated on disks by using a mirroring technique similar to what I discussed previously in this chapter. However, the mirroring technique is more sophisticated in that data is mirrored onto two or three disks at a time. Like standard mirroring, this approach has its advantages and disadvantages. If a storage space has two or three disks, you are fully protected against a single disk failure, and if a storage space has five or more disks, you are fully protected against two simultaneous disk failures. The disadvantage is that mirroring reduces capacity by up to 50 percent. For example, if you mirror two 1-TB disks, the usable space is 1 TB.

? Parity With a parity layout, data and parity information are striped across physical disks by using a striping-with-parity technique similar to what I discussed previously in this chapter. Like standard striping with parity, this approach has its advantages and disadvantages. You need at least three disks to fully protect yourself against a single disk failure. You lose some capacity to the striping, but not as much as with mirroring.

You can create a virtual disk in a storage pool by completing the following steps:

1. In Server Manager, select the File And Storage Services node, and then select the related Storage Pools subnode.

2. Select Tasks in the Virtual Disks panel, and then select New Virtual Disk. This starts the New Virtual Disk Wizard.

3. On the Storage Pool page, select the storage pool in which you want to create the virtual disk, and then click Next. Each available storage pool is listed according to the server it is managed by and available to. Make sure the pool has enough free space to create the virtual disk.

TIP Select the storage pool for the server you want to associate the virtual disk with and allocate storage from. For example, if you are configuring storage for CorpServer38, select a storage pool that is available to CorpServer38.

4. On the Specify The Virtual Disk Name page, enter a name and description for the virtual disk. If you are using a combination of SSD storage and HDD storage, use the check box provided to specify whether you want to create storage tiers. With storage tiers, the most frequently accessed files are automatically moved from slower HDD to faster SSD storage. This option is not applicable when the server has only HDD or SSD storage. To continue, click Next.

5. On the Select The Storage Layout page, select the storage layout as appropriate for your reliability and redundancy requirements. The simple layout is the only option for storage pools that contain a single disk. If the underlying storage pool has multiple disks, you can choose a simple layout, a mirror layout, or a parity layout. Click Next.

REAL WORLD If there aren’t enough available disks to implement the storage layout, you’ll get the error: The storage pool does not contain enough physical disks to support the selected storage layout. Select a different layout or repeat this procedure and select a different storage pool to work with initially.

? Keep in mind the storage pool might have one or more disks allocated as hot spares. hot spares are made available automatically to recover from disk failure when you use mirroring or parity volumes-and cannot otherwise be used. To force Windows to use a hot spare, you can remove the hot spare from the storage pool by pressing and holding or right-clicking it and selecting Remove, and then adding the drive back to the storage pool as an automatically allocated disk by pressing and holding or right-clicking the storage pool and selecting Add Physical Drive. Unfortunately, doing so might cause a storage pool created with a hot spare to report that it is in an Unhealthy state. If you subsequently try to add the drive again in any capacity, you’ll get an error stating “Error adding task: The storage pool could not complete the operation because its configuration is read-only.” The storage pool is not, in fact, in a read-only state. If the storage pool were in a read-only state you could enter the following command at an elevated Windows PowerShell prompt to clear this state:

Get-Storagepool "PoolName" | Set-Storagepool -IsReadonly $false

? However, entering this command likely will not resolve the problem. To clear this error, I needed to reset Storage Spaces and the related subsystem. You might find it easier to simply restart the server. After you reset or restart the server, the storage pool will transition from an error state (where a red circle with an ‘x’ is showing) to a warning state (where a yellow triangle with an ‘!’ is showing). You can then remove the physical disk from the storage pool by pressing and holding or right-clicking it and selecting Remove. Afterward, you will be able to add the physical disk as an automatically-allocated disk by pressing and holding or right-clicking the storage pool and selecting Add Physical Drive.

6. On the Specify The Provisioning Type page, select the provisioning type. Storage can be provisioned in a thin disk or a fixed disk. With thin-disk provisioning, the volume uses space from the storage pool as needed, up to the volume size. With fixed provisioning, the volume has a fixed size and uses space from the storage pool equal to the volume size. Click Next.

7. On the Specify The Size Of The Virtual Disk page, use the options provided to set the size of the virtual disk. With fixed provisioning, selecting Maximum Size ensures that the disk is created and sized with the maximum space possible given the available space. For example, if you use a 2-TB disk and a 1.5-TB disk with a mirrored layout, a 1.5-TB fixed disk will be created because this is the maximum mirrored size possible.

8. When you are ready to continue, click Next. After you confirm your selections, click Create. The wizard tracks the progress of the disk creation. When the wizard finishes creating the disk, the View Results page will be updated to reflect this. Review the details to ensure that all phases were completed successfully. If any portion of the configuration failed, note the reason for the failure and take corrective actions as appropriate before repeating this procedure.

9. When you click Close, the New Volume Wizard should start automatically. Use the wizard to create a volume on the disk as discussed in the following section.

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