Cache Switch To CacheMem Test

An access path is a path through which data and commands are transferred within a disk subsystem. Since data is written to the cache memory via a cache switch, the cache switch to cache memory route is also an access path. If there are too many writes still pending to the cache memory, you might want to know how the data transfer in this path is progressing to determine whether a slowdown in the path could have contributed to the high write-pending rate. This test monitors the usage of each cache switch to cache memory access path to facilitate such an analysis.

Target of the test : A Hitachi USP storage device

Agent deploying the test : A remote agent

Outputs of the test : One set of results for every cache switch to cache memory access path on the Hitachi USP device monitored.

Configurable parameters for the test
Parameter Description

Test Period

How often should the test be executed.

Host

The IP address of the host for which this test is to be configured.

Port

The port at which the specified host is listening. By default, this is set to NULL.

UserID, Password and Confirm password

The test should be configured with the credentials of a special user account, which is specifically created for use with the export utility; this account should fulfill the following conditions:

  • Should not possess the ‘write’ permission;
  • Can be of any user type; however, to ensure that the eG agent collects statistics pertaining to all storage partitions, it is recommended that this user is of type storage administrator;

Provide the credentials of this user against the UserID and Password parameters. Confirm the password by retyping it in the Confirm Password text box.

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 3 seconds.
Measurements made by the test
Measurement Description Measurement Unit Interpretation

Short CSWCMA

Indicates the percentage usage of this cache switch to cache memory access path.

Percent

A very high value or a value close to 100% for this measure could indicate that the access path is over-utilized, probably owing to a slow data write rate to the cache. Comparing the value of this measure across paths could indicate which path(s) is choking.

Data could be transferred slowly over a path if cache does not have enough space to accommodate the data. Such an event could occur if the cache is unable to write data to the disk quickly; a slowdown in writes to disk can severely hamper the cache’s ability to make space for data waiting to be written, thus crowding the access path.