We would like to thank Jerry B. Altzman for his initial input into the design of the index table. We thank John Heidemann for offering clarification regarding his previous work in the area of stackable filing. Thanks go to the Usenix reviewers and especially our shepherd, Margo Seltzer. This work was supported in part by NSF CISE Research Infrastructure grant EIA-9625374, an NSF CAREER award, and Sun Microsystems.