About the effects of L2ARC

Brendan Gregg wrote a good piece about the performance of L2ARC in ZFS L2ARC:

The pool_0 disks are still serving some requests (in this output 30 ops/sec) but the bulk of the reads are being serviced by the L2ARC cache devices - each providing around 2.6K ops/sec. The total delivered by this ZFS pool is 15.8K ops/sec (pool disks + L2ARC devices), about 8.4x faster than with disks alone.


Our average service time is between 0.4 and 0.6 ms (wsvt_t + asvc_t columns), which is about 20x faster than what the disks were delivering.