This statistic shows the size of the primary filesystem cache, the DRAM based ZFS ARC.
An understanding of ZFS ARC internals may be required to properly interpret this statistic.
When examining the effectiveness of the ARC on the current workload. The ARC should automatically increase in size to fill most of available DRAM, when enough data be accessed by the current workload to be placed in the cache. The breakdown allows the contents of the ARC to be identified by type.
This may also be checked when using cache devices (L2ARC) on systems with limited DRAM, as the ARC can become consumed with L2ARC headers.
If there are ARC caching issues on the appliance, also check the Cache: ARC accesses statistic to see how well the ARC is performing, and the Protocol statistics to understand the requested workload.
ARC component types: