Storage virtualization basically involves doing two things:
Taking physical storage devices and creating virtual pools of storage from them.
Provisioning shared storage from these pools as the need arises.
For example, a storage-virtualization solution might allow you to pool together several internal and externally-connected hard drives into a single pool of storage. You could then provision portions of this storage for your various file servers without needing to be concerned about which drives are being used by each file server or where on the drives any particular data is being stored. The benefits of this approach are obvious to experienced administrators and include the following:
Increased flexibility You can create new pools and expand existing ones without adding any new physical storage devices.
Increased scalability Additional physical storage can easily be added and used when needed to meet increasing business demands.
Increased elasticity You can pre-allocate storage capacity by using thin provisioning. Capacity can be increased to meet growing demand even when the underlying physical storage is insufficient.
Increased efficiency You can reclaim storage capacity when it is no longer needed to use physical storage resources more efficiently.
Lower cost By using low-cost, commodity-based hard drives, you can create large pools of storage. These pools can easily meet the needs of small and midsized businesses.
Windows Server 2012 now includes support for storage virtualization through a new feature called Storage Spaces, which allows you to aggregate internal and external physical disks into pools of low-cost storage that can have different levels of resiliency. These pools are simple to administer, can be allocated either manually or automatically, can be delegated for administration purposes, and can be delivered using either thin or fixed provisioning.
To implement and use Storage Spaces, you first need to understand its basic concepts and terminology. The following is a list of terminology associated with Storage Spaces:
Storage Management Application Programming Interface (SMAPI) A collection of Windows Management Instrumentation (WMI) interfaces for platform-neutral and vendor-neutral management of storage that are included in Windows Server 2012 and in System Center 2012 Virtual Machine Manager (VMM).
Storage Management Provider (SMP) An interface that provides a mechanism for discovering, managing, and provisioning storage. Windows Server 2012 includes support for the following types of SMPs:
Storage Spaces provider This SMP is included in Windows Server 2012 and is used for implementing storage virtualization using Storage Spaces.
Storage Management Initiative Specification (SMI-S) providers These providers support the Storage Management Initiative Specification (SMI-S) standard of the Storage Network Industry Association (SNIA) and can be used for platform-neutral and vendor-neutral implementation of storage virtualization using third-party storage solutions such as SANs.
Storage subsystem Uses an SMP to expose physical storage devices so that they can be virtualized into storage pools.
Storage pool A collection of physical disks that can be used to create virtual disks. A single storage pool can consist of physical disks having different sizes and using different storage interconnects. For example, you could mix and match Small Computer System Interface (SCSI) and Serial Attached SCSI (SAS) hard drives to create a pool.
You can create and delete storage pools to manage virtualized storage in your environment. Each physical disk can be included in only one storage pool at a time, and once you add a physical disk to a pool, the disk is no longer exposed in Disk Management for directly creating partitions or volumes on.
Primordial storage pool The default pool that contains all physical storage devices in a storage system that the Storage Spaces provider is able to enumerate, regardless of whether these devices have been added to other pools or not. Physical disks are displayed in the primordial pool only when they have no partitions or volumes created on them. If there are no available unused disks connected to your file server, the primordial pool is not displayed in Server Manager.
Virtual disk A logical unit number (LUN) that has been provisioned from a storage pool. Virtual disks behave like physical disks but have increased flexibility, scalability, and elasticity because they represent virtualized storage instead of physical storage. Virtual disks are also sometimes referred to as spaces.
Volume A portion of a virtual disk that has been formatted with a file system such as NTFS.
Share A folder in the file system of a volume that has been made accessible over the network to users who have appropriate permissions.
Dynamic disks and Storage Spaces
In previous versions of Windows Server, you could use dynamic disks for implementing software RAID 0 or RAID 1 redundancy for both the boot volume and data volumes. Dynamic disks were first introduced in Windows Server 2003 and were implemented using the new Virtual Disk Service (VDS) API included in that platform. Beginning with Windows Server 2012, however, the VDS API was superseded by SMAPI. This means that dynamic disks are now considered deprecated for all usages except mirroring the boot volumes. Storage Spaces should now be used instead of dynamic disks when you need to provide resiliency for data volumes. In addition, the following tools that rely on the VDS APIs should also be considered deprecated:
DiskPart command
DiskRAID command
Disk Management MMC snap-in
Note that you can still use these commands on Windows Server 2012, but they will not work with Storage Spaces or with any SMAPI components or tools.
