Wafl Iron: Repairing Live Enterprise File Systems

Consistent and timely access to an arbitrarily damaged file system is an important requirement of enterprise-class systems. Repairing file system inconsistencies is accomplished most simply when file system access is limited to the repair tool. Checking and repairing a file system while it is open for general access present unique challenges. In this paper, we explore these challenges, present our online repair tool for the NetApp (R) WAFL (R) file system, and show how it achieves the same results as offline repair even while client access is enabled. We present some implementation details and evaluate its performance. To the best of our knowledge, this publication is the first to describe a fully functional online repair tool.