Hi logback-dev, Thanks for bringing up logback 0.9.17. There are some new features we've desired for. It looks like SizeBasedTriggeringPolicy is not effecient enough because of using File.length() to check the active file size. And we think logback could improve this component to minimize the overhead. The jira ticket is here, which also includes a performance testing result for SizeBasedTriggeringPolicy. http://jira.qos.ch/browse/LBCORE-115 Thanks, Tom