Write Back Cache
When you create a new storage volume in Windows Server 2012 R2, you also have the option to enable something called the Write Back Cache. This feature sets aside an amount of physical storage, typically on a fast SSD drive, to use as a write cache to help smooth out the ups and downs of I/O during write- intensive operations. This can be seen in a typical database scenario where a large volume of disk writes may exceed the ability of the drive controller and disks to keep up. The cache would eliminate any pauses caused by an overwhelmed storage subsystem.