At the moment dafilesrvs transaction throttling treats most transactions equally.

The throttling kicks in if there are the # of concurrent transactions exceeds a configured limit.

Most of these transactions are expected to be quick, e.g. fileopen, size, read/write, close.

However 1 transaction, file copying, is vastly slower than the rest, but nevertheless takes up a throttle slot like the rest.
Consequently backed up file copies can drown out normal quick dafilesrv requests when throttling is on.

Throttling on file copies should be treated separately.

Should also:
1) improve handling of transactions that exceed the limit. As it stands blocked transactions can block the select handler or accept handler, therefore potentially blocking other minor traffic unnecessarily.
2) Improve stats on throttling and client info.
3) Improve error reporting back to client