Storage pools and storage spaces help reduce administrative overhead of managing separate physical storage arrays. Fewer moving parts correlate to lower administra- tive costs and in many situations fewer headaches. Secondly, storage pools provide more granular administrative control as they can take advantage of Access Con- trol Lists (ACLs) for the purpose of delegated administration. This is particularly helpful if you need to present a portion of the pool to different servers or separate administrators.
Scalability
Storage pools and storage spaces provide a more scalable solution over legacy stor- age strategies. The use of virtual disks allows for easier data migrations, which in many cases can occur in a nondisruptive manner.
Furthermore, unlike traditional physical disks, storage pools allow for dynamic expansion. If you are running low on space or if your pool dries up, additional stor- age can be added to the pool with little effort. Physical storage can be added or mixed from a variety of disk types, whether 10,000/15,000 RPM SATA drives, solid state, and so on, depending on your performance and capacity needs. The following disk types and configurations are supported:
■ Serial attached drives such as SCSI or SAS
■ SATA drives
■ JBOD enclosures
■ RAID enclosures with disabled RAID functionality
■ USB-attached drives
■ Clustered storage appliances
■ Physical disks must be at least 4 GB
ptg14504686 High Availability
Storage spaces can be designed and configured for high availability (HA) scenarios. Depending on the situation, storage pools can be designed using one of the configu- rations listed in Table 3-2 .
Table 3-2 Storage Space Configurations
Configuration Details Scenario
Simple Stripes data across physical disks. Used in situations where high availability is not required, but maximum storage and throughput are.
Mirror Requires a minimum of two physical disks to protect from a single disk failure and at least five physical disks to protect from two disk failures. As data is written, a duplicate copy is striped across multiple drives. Storage capacity is reduced with the increased redundancy.
Windows Server 2012 R2 now enables the use of parity space for failover clusters.
The default and most commonly used configuration.
Parity Requires a minimum of three physical disks to protect from a single disk failure. Data and parity information is striped across physical disks. Takes advantage of data journaling to keep track of the writes should an unplanned shutdown occur.
Used in scenarios that use sequential write methods such as a backup to disk solution. Due to its journaling feature, this is often used in scenarios in which you need to reduce chances of data corruption.
Dual Parity Introduced under Windows Server 2012 and continued in Windows Server 2012 R2, dual parity provides the ability to add disks to store additional parity information.
Used when you need to protect from two simultaneous disk failures.
Storage Tiers Windows Server 2012 R2 provides the ability to mix different disk types within a single disk enclosure, such as a JBOD, to create a cost-effective, tiered storage solution.
Tiered storage enables frequently accessed data to be automatically and transparently moved to faster drives such as solid state drives while data that is infrequently accessed is moved to slower, less costly disks such as high-capacity SATA drives.
ptg14504686 Configuration Details Scenario
Write-back cache Server 2012 R2 includes a write- back cache option that leverages solid state drives present in the configured storage space.
Used to increase protection and data loss due to power failures or lags in disk write activity. In a large environment, small random writes hammer away at the disk. To speed up the write process, solid state drives can be used as a write buffer to keep up with the random access workload.
Configuration of storage pools and virtual disks is discussed later in this chapter. Configuring Basic and Dynamic Disks
Now that you have an understanding of storage spaces and storage pools, let’s take a few moments to review the basics. When you first install Windows Server 2012 R2, the hard disk on which you install Windows is set up as a basic disk . When you add a new hard disk to your computer, this disk is also recognized as a basic disk. This disk type is the one that has existed ever since the days of MS-DOS. Starting with Win- dows 2000, Microsoft offered a new type of disk called a dynamic disk . This disk type offers several advantages over the basic disk, including the following:
■ You can create specialized disk volumes on a dynamic disk, including spanned,
striped, mirrored, and RAID-5 volumes. Basic disks are limited to primary and extended partitions and logical drives.
■ You can work with and upgrade disk volumes on-the-fly, without the need to
reboot your computer.
■ You can create an almost unlimited number of volumes on a dynamic disk.
A basic disk can only hold a total of four primary partitions or three primary partitions plus one extended partition.
Dynamic disks have their disadvantages, however:
■ The disk does not contain partitions or logical drives and therefore can’t be
read by another operating system.
■ On a multiboot computer, the disk might not be readable by legacy operating
systems.
ptg14504686 As with previous versions of Windows Server, there will be times when an admin-
istrator needs to make changes to one or more of the disks. For Windows Server 2012 R2, Microsoft has retained the Disk Management snap-in for the Computer Management console. As shown in Figure 3-1 , Disk Management is your primary tool for managing and configuring both physical and virtual disks. Configuring disks through Disk Management is covered in more detail in the proceeding sections.
Figure 3-1 Computer Management > Disk Management.
The volume properties of a disk, as displayed in Figure 3-1 , provide you with a sta- tus display that can help you in troubleshooting disk problems. The following vol- ume statuses can appear:
■ Healthy: This status is normal and means the volume is accessible and operat- ing properly.
■ Active: This status is also normal. An active partition is a partition or volume on a hard disk that has been identified as the primary partition from which the operating system is booted.
■ Failed: This status means the operating system could not start the volume normally. Failed usually means the data is lost because the disk is damaged or the file system is corrupted. To repair a failed volume, physically inspect the computer to see whether the physical disk is operating. Ensure that the under-
ptg14504686 ■ Formatting: This status is temporary, appearing only while the volume is
being formatted.
■ Unknown: This status means you’ve installed a new disk and have not cre- ated a disk signature or that the boot sector for the volume is corrupt, pos- sibly because of a virus. You can attempt to repair this error by initializing the underlying disk by right-clicking the disk and selecting Initialize from the shortcut menu.
■ Data Incomplete: This status appears when a disk has been moved into or out of a multidisk volume. Data is destroyed unless all the disks are moved and imported on the new computer.
■ Healthy (At Risk): This status indicates I/O errors have been detected on an underlying disk of the volume but that data can still be accessed. The underly- ing disk probably shows a status of Online (Errors) and must be brought back online for the volume to be corrected.