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A Docker server can have multiple images using which containers are created. In large environments where the requirements of users vary from minute to minute, it is important for an administrator to cater to their specific needs by providing the images of their choice so that the users can create the containers and load applications accordingly. Often administrators may be confused while identifying the needs of the users. An image that is needed today may not be needed tomorrow to create a container. In such cases, the images may be unutilized but still hold on valuable disk space. To optimize the disk space and eliminate unused images, administrators are required to analyze the performance of the images as well as identify the images that are most commonly used by the users. The DockImgPerfTest test helps administrators in this regard!

This test monitors the images of the Docker server and reports the number of containers created using each image. By analyzing the number of running containers created from each image and the resource utilization of those containers, administrators can figure out the image that is widely used by the users to create the containers and analyze how well the resources are utilized by those containers.

Outputs of the test : One set of results for each image available on the target Docker server that is being monitored

Measurement	Description	Measurement Unit	Interpretation
Container_count	Indicates the total number of containers that were mapped to this image.	Number	The detailed diagnosis of this measure if enabled, lists the name of the containers. Compare the value of this measure across the images to identify the image to which maximum number of containers are mapped.
Running_container	Indicates the number of containers that are created from this image and are currently in Running state.	Number	Ideally, the value of this measure should be high. A low value for this measure is a cause of concern. The detailed diagnosis of this measure if enabled, lists the containers that are currently in Running state and the resource utilization of the containers.
CPU_util	Indicates the percentage of CPU utilized by the containers (created from this image) that are currently in Running state.	Percentage	This measure is only applicable for the Docker server 1.5 and above. A sudden increase or decrease in the value of this measure could be a cause for concern.
Memory_used	Indicates the amount of memory utilized by the containers (created from this image) that are currently in Running state.	MB	This measure is only applicable for the Docker server 1.5 and above. A low value is desired for this measure. A high value of this measure indicates that the Docker is running out of space.
Memory_util	Indicates the percentage of memory utilized by the containers (created from this image) that are currently in Running state.	Percentage	This measure is only applicable for the Docker server 1.5 and above. A value close 100% indicates that the memory is running out of space.
Image_size	Indicates the amount of disk space utilized by this image.	MB	Ideally, the value of this measure should be low. A significant increase in the value of this measure could be a cause of concern.