SAS expander-based SAS/SATA bridging

Described herein is an improved mechanism for bridging between SAS and SATA drives based upon existing SAS expanders in a SAS domain. In particular, a bridge capable of translating between SAS and SATA protocols is embedded in or coupled to an expander. When a SAS initiator request is received at the expander, the expander can route the request, based on a routing table, either directly to a destination SAS device or to the bridge for necessary translation before it is transmitted to a destination SATA drive. The routing table includes corresponding relationships between all SAS addresses and Phys through which those SAS and SATA devices are attached to the expander. SATA devices can be virtualized in the expander through a few assigned addresses in the routing table in a SAS discovery process.