If the working set of the storage system is very large, such as a large E-mail server, you can cache only system metadata in FlexScale memory by turning off both normal user data block caching and low-priority user data block caching.
When you cache only system metadata, with both flexscale.normal_data_blocks and flexscale.lopri_data_blocks set to off, the WAFL extended cache interprets this setting as the buffer cache policy of reuse and does not save normal data blocks or low-priority blocks in the extended cache.