Traffic recordings already have a maxSize (idl, checked in traffic_recorder.cpp).

For shadow clusters, we anticipate large recordings spanning a reasonable amount of time.

Additionally, we anticipate needing to incrementally store and retrieve parts of the recording, as the total size may be larger than is practical to store on disk concurrently.

Based on this, we will repurpose the maxSize as the max file size, and should close the current file, and open a new one in the same directory.

SERVER-103220 may change the name of this limit, and will also change the argument filename to directory, but will not alter the handling of the argument. Here in this ticket, the semantics should change; the argument should be validated to be a directory, and the recording files opened within that directory.
SERVER-104217 introduces checksums, which should be per file, not for the entire recording.