What's New in Storage Spaces in Windows Server


Updated: July 3, 2014

Applies To: Windows Server 2012 R2

This topic describes the features that were added to Storage Spaces in Windows Server 2012 R2, including storage tiers, write-back cache, and dual parity.

Storage Spaces enables cost-effective, high availability, scalable, and flexible storage solutions for virtual or physical deployments. Storage Spaces delivers sophisticated storage virtualization capabilities that empower customers to use industry-standard storage for scalable multinode deployments or single server deployments. It is appropriate for a wide range of customers, including enterprise and cloud hosting companies that use Windows Server for high availability and scalable storage that is cost effective. For more information, see Storage Spaces Overview and Software-Defined Storage Design Considerations Guide.

The following table describes the changes in Storage Spaces functionality that are available in this release.


New or updated?


Storage tiers


Automatically moves frequently accessed data to faster (solid-state drive) storage and infrequently accessed data to slower (hard disk) storage.

Write-back cache


Buffers small random writes to solid-state drives, reducing the latency of writes.

Parity space support for failover clusters


Enables you to create parity spaces on failover clusters.

Dual parity


Stores two copies of the parity information on a parity space, which helps protect you from two simultaneous physical disk failures and optimizes storage efficiency.

Automatically rebuild storage spaces from storage pool free space


Decreases how long it takes to rebuild a storage space after a physical disk failure by using spare capacity in the pool instead of a single hot spare.

With Storage tiers, you can create virtual disks that are comprised of two tiers of storage:

  • Solid-state drive tier for frequently accessed data

  • Hard disk drive tier for less-frequently accessed data

Storage Spaces transparently moves data at a subfile level between the two tiers, based on how frequently data is accessed.

What value does this change add?

Storage tiers combine the best attributes of solid-state drives and hard disk drives. They increase the performance of the most used (“hot”) data by moving it to solid-state drives, without sacrificing the ability to store large quantities of data on inexpensive hard disks.

What works differently?

The following aspects work differently with storage tiers:

  • To create a storage space with storage tiers, the storage pool must have a sufficient number of hard disks and solid-state drives to support the selected storage layout, and the hard disks must contain enough free space.

  • When you create a storage space by using the New Virtual Disk Wizard or the New-VirtualDisk cmdlet, you can specify to create the virtual disk with storage tiers.

  • To create a storage space with storage tiers, the virtual disk must use fixed provisioning, and the number of columns will be identical on both tiers (a four-column, two-way mirror with storage tiers would require eight solid-state drives and eight hard disk drives).

  • Volumes that are created on virtual disks that use storage tiers should be the same size as the virtual disk.

  • Administrators can pin (assign) files to the standard hard disk drive tier or to the faster solid-state drive tier by using the Set-FileStorageTier cmdlet. This ensures that the files are always accessed from the appropriate tier.

  • There are the following new Windows PowerShell cmdlets for working with storage tiers, and the New-VirtualDisk cmdlet includes the –StorageTiers and -StorageTierSizes parameters.

    • Set-FileStorageTier

    • Get-FileStorageTier

    • Clear-FileStorageTier

    • New-StorageTier

    • Get-StorageTier

    • Set-StorageTier

    • Resize-StorageTier

    • Remove-StorageTier

    • Get-StorageTierSupportedSize

For information about using storage tiers, see: Step-by-step for Storage Spaces Tiering in Windows Server 2012 R2.

Storage Spaces can use existing solid-state drives in the storage pool to create a write-back cache that is tolerant of power failures and that buffers small random writes to solid-state drives before later writing them to hard disk drives.

What value does this change add?

Small random writes often dominate common enterprise workloads, and they can impact the performance of other data transfers that are taking place. By using solid-state drives (which excel at random access) for a write-back cache, Storage Spaces can reduce the latency of the random writes and also greatly reduce any impact on the performance of other data transfers.

What works differently?

The write-back cache is transparent to administrators and users, and it is created on all new virtual disks if there are a sufficient number of solid-state drives in the storage pool, as determined by the following requirements for the associated storage space:

  • Simple spaces require one solid-state drive

  • Two-way mirror spaces and single-parity spaces require two solid-state drives

  • Three-way mirror spaces and dual parity spaces require three solid-state drives

The write-back cache works with all types of storage spaces, including storage spaces with storage tiers.

Newly created storage spaces automatically use a 1 GB write-back cache by default when the storage pool contains enough physical disks with MediaType set to SSD or Usage set to Journal to support the specified resiliency setting. If there aren’t enough physical disks with these settings, the write-back cache size is set to 0, except for parity spaces, when it’s set to 32 MB.

With Storage Spaces, you can create parity spaces on failover clusters.

What value does this change add?

Workloads that require greater capacity utilization than mirror spaces can now use parity spaces with one or two copies of parity information (single or dual parity) to maximize capacity and resiliency, while still offering the ability to fail over to another cluster node.

What works differently?

The parity storage layout is an option when you create virtual disks in Server Manager or with the New-VirtualDisk cmdlet.

Dual parity stores two copies of parity information in a parity space, helping protect you from two simultaneous disk failures.

What value does this change add?

Dual parity enables you to keep a high level of resiliency when you use a parity space with a large number of disks or any time you need to help protect against two simultaneous disk failures.

What works differently?

The dual parity resiliency type is an option when you create virtual disks in Server Manager or with the New-VirtualDisk cmdlet.

Storage Spaces now includes the ability to automatically rebuild storage spaces from storage pool free space instead of using hot spares.

What value does this change add?

Rebuild times are accelerated because multiple disks in the pool can accept the data that was stored on the failed disk instead of waiting for a single hot spare to write all of the data. Additionally, hot spare drives are no longer needed, and storage pool free space can provide additional capacity and performance to the pool.

What works differently?

When a physical disk fails, instead of writing a copy of the data that was on the failed disk to a single hot spare, the data is copied to multiple physical disks in the pool so that the previous level of resiliency is achieved. Administrators no longer need to allocate physical disks as hot spares in the storage pool.