In Windows Server 2012 Microsoft introduced CSV Cache for Windows Server 2012 Hyper-V and Scale-Out File Server Clusters. The CSV Block Cache is basically a RAM cache which allows you to cache read IOPS in the Memory of the Hyper-V or the Scale-Out File Server Cluster nodes. In Windows Server 2012 you had to set the CSV Block Cache and enable it on every CSV volume. In Windows Server 2012 R2 CSV Block cache is by default enabled for every CSV volume but the size of the CSV Cache is set to zero, which means the only thing you have to do is to set the size of the cache.
# Get CSV Block Cache Size
# Set CSV Block Cache Size to 512MB
(Get-Cluster).BlockCacheSize = 512
Microsoft recommends using 512MB as cache on a Hyper-V host. On a Scale-Out File Server node, things are a little bit different. In Windows Server 2012 Microsoft allowed you to use a cache size up to 20% of the server, in Windows Server 2012 R2 Microsoft changed this, so you can now finally use up to 80% of the RAM of a Scale-Out File Server but with a maximum of 64GB.
Back in the days of Windows Server 2012 I made a little benchmark of CSV Cache on my Hyper-V hosts.