Here are a few links to some great references on optimizing SQL transaction log throughput. In particular, these articles discuss key tips regarding the sizing of transaction logs and the impact too many or too few virtual log files (VLFs) can have on overall performance:
8 Steps to better Transaction Log throughput
Transaction Log VLFs – too many or too few?
Bug: log file growth broken for multiples of 4GB
How to determine SQL Server database transaction log usage
Geek City: Exploring the Transaction Log Structure
Understanding Logging and Recovery in SQL Server