Web proxies are slowly convergent; it takes days to reach the maximal hit rate. Consequently, proxy cache contents must be saved across system failures. At the same time, recovery must be quick. With today's disk sizes, the system cannot wait for full disk scans before servicing document requests. Hummingbird warms the main memory cache with files and clusters that were ``hot'' before the system reboot. Bounding file create and delete persistence rather than attaching them to system call semantics allows for higher performance.