Rotational Lease: Providing High Availability in a Shared Storage File System

Shared storage file systems consist of multiple storage devices connected by dedicated data-only network and workstations that can directly access the storage devices. In this shared-storage environment, data consistency is maintained by lock servers which use separate control network to transfer the lock information. Furthermore, lease mechanism is applied to cope with control network failures. However, when the control network fails, participating workstations can no longer make progress after the lease term expires. In this paper we address this limitation and present a method that enables networkpartitioned workstations to continue file operations even after the control network is down. The proposed method works in a manner that each workstation is rotationally given a predefined lease term periodically. We also show that the proposed mechanism always preserves data consistency.