Exadata Flash Log Status Test

Exadata Smart Flash Logging, is the feature that writes to both hard disk and flash with the acknowledgement given as soon as either completes the write, thus improving response time and throughput.

Exadata Smart Flash Log reduces the average latency for performance-sensitive redo log write I/O operations, thereby eliminating performance bottlenecks that may occur due to slow redo log writes. Originally, Exadata Smart Flash Log was used to perform simultaneous writes to disk and flash storage. However, a further optimization known as Smart Flash Log Write-Back, uses Exadata Smart Flash Cache in Write-Back mode instead of disk storage.

In the event that the Flash Cache writes the data faster, the data need to be held only for a short time until the storage server is certain that all writes have made it to the redo log. Since the Smart Flash Log is only a temporary store, only a small amount of Flash cache is required—512MB per cell. If the flash logging feature is unavailable or could not be enabled, then the I/O operations to the redo log may slow down considerably thereby leading to performance bottlenecks. To eliminate such bottlenecks, it is it is necessary to keep track on the status of the flash log. The Exadata Flash Log Status test helps administrators to keep a vigil on the flash log!

This test auto-discovers the flash logs on the target storage server and for each flash log reports the status. This test also reveals the cell disks that are allocated to each flash cache and those cell disks that are unavailable. In addition, this test also reveals the size of the flash cache that is available for use. Using this test, administrators can figure out those flash caches that are in a critical state, isolate them and fix issues proactively. Also, administrators can figure out the flash cache that is currently being most utilized.

Target of the test : Oracle Exadata Storage Server

Agent deploying the test : A remote agent

Outputs of the test : One set of the results for the target Oracle Exadata Storage Server that is being 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 number at which the specified host listens. By default, this is NULL.
Username, Password and Confirm Password	By default, this test uses the Cell Control Command-Line Interface (CellCLI) to pull out the required metrics. To use the CLI, the test first needs to connect to the target storage server via SSH, and then run commands using CLI. For running the commands, this test requires the credentials of a cellmonitor user. Specify the login 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.
SSH Port	This test uses the Cell CLI to pull metrics from the target Oracle Exadata Storage Server. To run the CLI commands, this test first needs to establish an SSH connection with the target storage server. To enable the test to establish this connection, specify the SSH Port here.
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 120 seconds.
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
Flash log status	Indicates the current status of this flash log.		The table below indicates the values that this measure can report and their corresponding numeric equivalents: Measure value Numeric Value Normal 100 Warning 90 Critical 50 Note: By default, this measure reports the above-mentioned Measure Values while indicating the current status of the flash log. However, in the graph of this measure, the status of the flash log will be represented using the corresponding numeric equivalents only.
Cell disks	Indicates the number of cell disks allocated to this flash log.	Number	The detailed diagnosis of this measure lists the names of the cell disks that are allocated to the flash log.
Flash log size	Indicates the total size of this flash log.	GB
Usable flash log size	Indicates the amount of space that is available for use in this flash log.	GB
Flash log efficiency	Indicates the percentage of space that is available for use in this flash log.	Percent	A value close to 0 indicates that the flash cache is running out of space.
Unavailable cell disks	Indicates the number of cell disks that are currently unavailable for this flash log.	Number