Which volume configuration specifically sets a maximum size of 40000 MB?

The volume configuration identified as [volume:one] is the correct answer because it explicitly sets a maximum size limit for that volume to 40000 MB. In Splunk, volume configurations are used to define the properties and constraints of indexed data storage. By specifying attributes such as the maximum size in the configuration file, administrators can manage storage effectively, ensuring that no single volume exceeds the defined limit, which is essential for efficient resource allocation and performance.

In the context of other options, if they were to potentially define different volume settings, they would not have the specified maximum size of 40000 MB, thus making them less relevant in this scenario. This specificity in the configuration helps in maintaining operational stability by preventing excessive data accumulation in any single volume.