The Flash Pool aggregate technology provides both read caching and write caching for random I/O workloads. You can configure Flash Pool aggregate caching on the volume, but for most workloads, the default caching policies result in optimal performance.
Some volumes cannot be enabled for write caching. When you attempt to use an aggregate associated with one or more of these volumes as a Flash Pool aggregate, you must force the operation. In this case, writes to that volume would not be cached in the SSD cache, but otherwise the Flash Pool aggregate would function normally. You can get more information about why a volume cannot be enabled for write caching by using the vol status -v command.
For more information about read and write caching policies, see Technical Report 4070: NetApp Flash Pool Design and Implementation Guide.