- Oracle ZFS Storage Appliance Analytics Guide, Release OS8.8.x
- Working with Analytics
- When to Add the First Read Cache Device (CLI)
When to Add the First Read Cache Device (CLI)
Use the following procedure to determine if you need a first read cache device for Oracle ZFS Storage Appliance. To determine if you need more than one device, see When to Add More Read Cache Devices (CLI).
- Create a worksheet as described in Creating a Worksheet (CLI), select that worksheet, and then enter
dataset
.hostname:analytics worksheets> select worksheet-000 hostname:analytics worksheet-000> dataset
- Enter
set name=arc.accesses[hit/miss]
, and then entercommit
to add cache ARC access broken down by hit/miss to your worksheet.hostname:analytics worksheet-000 dataset (uncommitted)> set name=arc.accesses[hit/miss] name = arc.accesses[hit/miss] hostname:analytics worksheet-000 dataset (uncommitted)> commit
- Enter
dataset
.hostname:analytics worksheet-000> dataset
-
Repeat steps 2 and 3 to add the following datasets:
-
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
-
- Enter
done
, and then enterdone
again to exit the context.hostname:analytics worksheet-000> done hostname:analytics worksheets> done
- Wait several minutes, and then go to
analytics datasets
.Note:
This wait time can be adjusted to better determine your peak I/O. Capturing analytics for 24 hours during normal business operations may reveal the best understanding of your I/O patterns.hostname:> analytics datasets
- Enter
show
to view a list of available 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>
- Enter
select
and the dataset with the namearc.accesses[hit/miss=metadata hits][L2ARC eligibility]
.In this example, dataset name
arc.accesses[hit/miss=metadata hits][L2ARC eligibility]
corresponds todataset-001
.hostname:analytics datasets> select dataset-001
- Enter
read 86400
to read the last 86,400 seconds, or 24 hours, of the dataset. When you are finished examining the data, enterdone
.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
-
Oracle ZFS Storage Appliance has an active filesystem or LUN with a ZFS recordsize of 32 k or smaller
-
- Enter
show
to view a list of available 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] dataset-002 active 780K 9.20M arc.accesses[hit/miss=data hits][L2ARC eligibility] ... hostname:analytics datasets>
- Enter
select
and the dataset with the namearc.accesses[hit/miss=data hits][L2ARC eligibility]
.In this example, dataset name
arc.accesses[hit/miss=data hits][L2ARC eligibility]
corresponds todataset-002
.hostname:analytics datasets> select dataset-002
- Enter
read 86400
to read the last 86,400 seconds, or 24 hours, of the dataset. When you are finished examining the data, enterdone
.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
-
Oracle ZFS Storage Appliance has an active filesystem or LUN with a ZFS recordsize of 32 k or smaller
-