Use the following procedure to determine if you need a first read cache device for the appliance. To determine if you need more than one device, see When to Add More Read Cache Devices (CLI).
hostname:analytics worksheets> select worksheet-000 hostname:analytics worksheet-000> dataset
hostname:analytics worksheet-000 dataset (uncommitted)> set name=arc.accesses[hit/miss] name = arc.accesses[hit/miss] hostname:analytics worksheet-000 dataset (uncommitted)> commit
hostname:analytics worksheet-000> dataset
Cache ARC accesses broken down by metadata hits and misses ("arc.accesses[hit/miss=metadata hits][L2ARC eligibility]")
Cache ARC accesses broken down by data hits and misses ("arc.accesses[hit/miss=data hits][L2ARC eligibility]")
hostname:analytics worksheet-000 dataset (uncommitted)> set name="arc.accesses[hit/miss=metadata hits][L2ARC eligibility]" name = arc.accesses[hit/miss=metadata hits][L2ARC eligibility] hostname:analytics worksheet-000 dataset (uncommitted)> commit hostname:analytics worksheet-000> dataset hostname:analytics worksheet-000 dataset (uncommitted)> set name="arc.accesses[hit/miss=data hits][L2ARC eligibility]" name = arc.accesses[hit/miss=data hits][L2ARC eligibility] hostname:analytics worksheet-000 dataset (uncommitted)> commit
hostname:analytics worksheet-000> done hostname:analytics worksheets> done
hostname:> analytics datasets
hostname:analytics datasets> show Datasets: DATASET STATE INCORE ONDISK NAME dataset-000 active 1.27M 15.5M arc.accesses[hit/miss] dataset-001 active 517K 9.21M arc.accesses[hit/miss=metadata hits][L2ARC eligibility] ... hostname:analytics datasets>
In this example, dataset name arc.accesses[hit/miss=metadata hits][L2ARC eligibility] corresponds to dataset-001.
hostname:analytics datasets> select dataset-001
hostname:analytics dataset-001> read 86400 ... hostname:analytics dataset-001> done
Consider adding the first read cache device when all of the following conditions are present:
There are at least 1500 L2ARC-eligible ARC access misses for metadata per second
The appliance has an active filesystem or LUN with a ZFS recordsize of 32k or smaller
hostname:analytics datasets> show Datasets: DATASET STATE INCORE ONDISK NAME dataset-000 active 1.27M 15.5M arc.accesses[hit/miss] dataset-001 active 517K 9.21M arc.accesses[hit/miss=metadata hits][L2ARC eligibility] dataset-002 active 780K 9.20M arc.accesses[hit/miss=data hits][L2ARC eligibility] ... hostname:analytics datasets>
In this example, dataset name arc.accesses[hit/miss=data hits][L2ARC eligibility] corresponds to dataset-002.
hostname:analytics datasets> select dataset-002
hostname:analytics dataset-002> read 86400 ... hostname:analytics dataset-002> done
Consider adding the first read cache device when all of the following conditions are present:
There are at least 1500 L2ARC-eligible ARC access misses for data per second
The appliance has an active filesystem or LUN with a ZFS recordsize of 32k or smaller