Oracle ZFS ARC Accesses Test

The ARC is the Adaptive Replacement Cache and is an in-DRAM cache for file system and volume data. This test monitors the accesses to the ARC and reports performance issues in the ARC, if any. This test also helps to understand how well the current workload is caching in the ARC.

Target of the test : Oracle ZFS Storage System

Agent deploying the test : A remote agent

Outputs of the test : One set of results for the Oracle ZFS Storage System being monitored.

Configurable parameters for the test
Parameter	Description
Test period	How often should the test be executed.
Host	The IP address of the target system that is being monitored.
Port	The port number through which Oracle ZFS Storage System communicates. The default port is 215.
User, Password and Confirm Password	By default, this test uses the REST API commands to pull out the required metrics. To execute the REST API commands, the eG agent requires the permission of a local administrator user who has been assigned with Basic role and a custom role with Analytics authorization and read permission. Specify the credentials of such a user in the USERNAME and PASSWORD text boxes and confirm the Password by retyping it in the CONFIRM PASSWORD text box. To create a new user with the required permissions, refer Creating a new user on Oracle ZFS Storage System.
Timeout	Specify the time duration for which this test should wait for a response from the storage system in the TIMEOUT text box. By default, this is 60 seconds.
Num DD Messages	By default, the NUM DD MESSAGES parameter is set to 10. This means that, by default, the detailed diagnosis of this test will report the details of the top-10 records of the measures that are obtained upon execution of this test. To view the details of more records as part of detailed metrics, you will have to increase the value of this parameter. Likewise, to view the details of less than 10 records, reduce the value of this parameter.
DD Frequency	Refers to the frequency with which detailed diagnosis measures are to be generated for this test. The default is 1:1. This indicates that, by default, detailed measures will be generated every time this test runs, and also every time the test detects a problem. You can modify this frequency, if you so desire. Also, if you intend to disable the detailed diagnosis capability for this test, you can do so by specifying none against DD frequency.
Detailed Diagnosis	To make diagnosis more efficient and accurate, the eG Enterprise embeds an optional detailed diagnostic capability. With this capability, the eG agents can be configured to run detailed, more elaborate tests as and when specific problems are detected. To enable the detailed diagnosis capability of this test for a particular server, choose the On option. To disable the capability, click on the Off option. The option to selectively enable/disable the detailed diagnosis capability will be available only if the following conditions are fulfilled: The eG manager license should allow the detailed diagnosis capability Both the normal and abnormal frequencies configured for the detailed diagnosis measures should not be 0.

Measurements made by the test
Measurement	Description	Measurement Unit	Interpretation
Average hit ratio	Indicates the ARC hit ratio during the last measurement period.	Percent	A high value is desired for this measure.
Average data hits	Indicates the average data hits during the last measurement period.	Hits/sec	Data hit occurs when a data block is in the ARC DRAM cache and had returned. A high value is desired for this measure. A very low value is a cause for concern.
Peak data hits	Indicates the peak data hit during the last measurement period.	Hits/sec	The detailed diagnosis shows when data requests had hit peaks.
Average data misses	Indicates the average data misses during the last measurement period.	Misses/sec	Data miss is when a data block is not in the ARC DRAM cache and is read from the L2ARC cache devices (if available and the data is cached on them) or the pool disks. A high value is desired for this measure. A very low value is a cause for concern.
Peak data misses	Indicates the peak data misses during the last measurement period.	Misses/sec	The detailed diagnosis shows when data requests had been unsuccessful thus causing degradation in performance.
Average metadata hits	Indicates the average metadata hits during the last measurement period.	Hits/sec	The term metadata refers to the “data about data” and is a concept utilized to store the data for all form modifications. This measure displays the average count of successful metadata requests.
Peak metadata hits	Indicates the peak metadata hits during the last measurement period.	Hits/sec	The detailed diagnosis shows when and how many metadata requests had been successful.
Average metadata misses	Indicates the average metadata misses during the last measurement period.	Misses/sec	A high value of this measure can cause performance degradation of the system and increases latency.
Peak metadata misses	Indicates the peak metadata misses during the last measurement period.	Misses/sec	The detailed diagnosis shows when and how many metadata requests had been unsuccessful.
Average prefetched data hits	Indicates the average prefetched data hits during the last measurement period.	Hits/sec	Prefetching is read-ahead caching. It lets the SP anticipate the data an application will request, so that it can read it from disk into its read cache before the data is needed. A high value is desired for this measure.
Peak prefetched data hits	Indicates the peak prefetched data hits during the last measurement period.	Hits/sec	The detailed diagnosis shows when and how many prefetched data requests had been successful.
Average prefetched data misses	Indicates the average prefetched data misses during the last measurement period.	Misses/sec	A high value of this measure can cause performance degradation of the system and increases latency.
Peak prefetched data misses	Indicates the peak prefetched data misses during the last measurement period.	Misses/sec	The detailed diagnosis shows when and how many prefetched data requests had been unsuccessful.