As storage systems grow larger and more complex, the traditional block-based design of current disks can no longer satisfy workloads that are increasingly metadata intensive. A new approach is offered by object-based storage devices (OSDs). By moving more of the responsibility of storage management onto each OSD, improvements in performance, scalability and manageability are possible. Since this technology is new, no physical object-based storage device is currently available. In this work we describe a software emulator that enables a storage server to behave as an object-based disk. We focus on the design of the attribute storage, which is used to hold metadata associated with particular data objects. Alternative designs are discussed, and performance results for an SQL implementation are presented.