Cache Statistics Test

The Array application delivery controller serves frequently requested content from cache for increased performance and to help scale the capacity for Web - based application services. The cache is said to be effectively utilized only if it is able to service the maximum number of requests; this greatly reduces direct disk accesses and related overheads, and thus improves performance. On the contrary, ineffective cache usage can be the key contributor to a slowdown or degradation in performance, as it increases disk accesses. To understand how the caches are utilized and to promptly capture abnormalities in cache usage, administrators have to continuously monitor the requests processed in the cache. This is what exactly the Cache Statistics test does!

This test continuously tracks the cache on the target delivery controller and reports the total number of requests that were received by the cache. In addition, this test also reveals the number of GET, HEAD, PURGE and POST requests that were received by the cache and the hit ratio of the cache. This way, administrator can figure out the ineffective request processing patterns of the cache, which may contribute to a slowdown in operations.

Target of the test : An Array Application Delivery Controller

Agent deploying the test : A remote agent

Outputs of the test : One set of results for the target Array Application Delivery Controller that is to be monitored.

Configurable parameters for the test

Parameter	Description
Test Period	How often should the test be executed.
Host	The IP address of the host that is being monitored.
SSH Username and SSH Password	Specify the credentials of a user who has the right to execute CLI (command-line interface) commands on the target delivery controller and pull out metrics via SSH.
Confirm Password	Confirm the SSH Password by retyping it here.
SSH Port	Specify the SSH port of the target delivery controller here; The default value is 22.
SSH Enable Password	The delivery controller offers three levels or modes to the ArrayOS. The modes are given below: User Mode - In this mode, user can perform the authorized and basic operations and non-critical functions. Enable Mode - When this mode is selected, the user can run majority of commands for view data. Config Mode - Using this level, the user can change the configuration of the delivery controller for global configuration and access (Using CLI commands). The SSH Enable password is the password that is needed for the user to access the commands when the Enable Mode is selected.
Confirm Password	Confirm the SSH Enable Password by retyping it here.
Timeout	Specify the duration (in seconds) within which the SNMP query executed by this test should time out in this text box. The default is 10 seconds.

Measurements made by the test

Measurement	Description	Measurement Unit	Interpretation
Requests received	Indicates the total number of requests received by the cache in the target delivery controller during the last measurement period.	Number
Requests with get method	Indicates the number of GET requests received by the cache during the last measurement period.	Number	Using the GET method, you can retrieve specific information from the cache. When the cache receives the GET request, it returns the requested data as the entity in response.
Requests with head method	Indicates the number of HEAD requests received by the cache during the last measurement period.	Number	The HEAD method is identical to GET except that the cache will not return a message-body in the response.
Requests with purge method	Indicates the number of PURGE requests received by the cache during the last measurement period.	Number	A purge is what happens when you pick out an object from the cache and discard it along with its variants. Usually a purge is invoked through HTTP with the method PURGE. HTTP Purge sends a request to delete the cached data of a page or post every time it it modified. This happens when updating, publishing, commenting on, or deleting an post HTTP Purge sends a request to delete the cached data of a page or post every time it modified. This happens when updating, publishing, commenting on, or deleting an post
Requests with post method	Indicates the number of POST requests received by the cache during the last measurement period.	Number
Hit ratio	Indicates the percentage of requests that were successfully retrieved from the cache during the last measurement period.	Percent