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What are write back cache's requirements?

Deploying larger, SSD-based write-back caches might require more than one disk. The benefits can lead to better performance.

It's important to note that Windows Server does not require solid-state disk drives for write back cache. When...

only traditional magnetic disks are deployed in a virtual disk (no solid-state disks are available), Windows Server can create a small, 32 MB write back cache in memory.

In order to deploy larger write back caches based on larger, solid-state disks, an organization will require Windows Server 2012 R2 and at least SSD. When a new virtual disk volume is created, administrators will have the option to create a 1 GB write-back cache on the SSD.

If cache must be created on high-resiliency servers configured with mirrored drives, additional SSDs may be needed. For example, two-way mirrors using single parity require two SSDs, while three-way mirrors using dual parity will need three SSDs.

Administrators can check the write-back cache status for every virtual disk on the server using the Get-VirtualDisk cmdlet in PowerShell. An example command line might look like this:

PS C:\Server1\Admin> Get-VirtualDisk | Select-Object FriendlyName, Size, WriteCacheSize

This command displays the name of each volume, its volume size and its cache size.

Write caching reduces application latency by making writes to fast memory instead of to a slower disk. It's a well-established technology, but has often been avoided because of the potential for catastrophic data loss. The adoption of SSD devices is quickly bringing write caching to the forefront, allowing inherently nonvolatile SSD space to serve as write cache. Windows Server 2012 R2 includes native support for SSD-based write-back caches, which can be created on demand as new virtual disks are provisioned for the enterprise. This offers administrators a new tool for accelerating busy, write-intensive, mission-critical workloads without the traditional concerns of expensive, battery-backed write caching subsystems.

Next Steps

Why write back cache can create performance boosts

Altering write back cache size

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