The L2ARC is the 2nd Level Adaptive Replacement Cache, and is an SSD-based cache that is accessed before reading from the much slower pool disks. The L2ARC is currently intended for random read workloads. This statistic shows the read and write byte rates to the L2ARC cache devices, if cache devices are present.
When to Check L2ARC I/O Bytes
Cache: L2ARC I/O Bytes statistic is useful to check during warmup. The write bytes will show the rate of L2ARC warmup time.
L2ARC I/O Bytes Breakdowns
Table 5-14 Breakdowns of L2ARC I/O Bytes
type of operation
Read or write. Read bytes are hits on the cache devices. Write bytes show the cache devices populating with data.
See also Cache: L2ARC Accesses.