What logging listener should be used in production? (ASP.NET / Logging Application Block)

I'm using MS Enterprise Logging Application Block in an ASP.NET website.

For production launch, I will set up a log listener in one of these locations:

• Sql Server database
• Windows event log
• Text files

Which has the least impact on performance?

NB - I can't switch to Log4Net or ELMAH at this point, so please don't suggest that in your response.

I ended up using this configuration in prod:

1. FormattedDatabaseTraceListener for messages with severity "error" and "critical".
2. Flat file trace listener for specialSources in case logging database is down.

Anything with lower severity, we are not logging.