Author: David Allen, Director of Strategic Marketing, Storage Products Division
Serial Attached SCSI (SAS) expander architectures provide flexible, cost-effective connections for internal and external storage subsystems in the mid-range and enterprise server markets. In this article we address SAS expanded architectures applicable to both server and storage enclosure applications.
Expander Types and Features
SAS Edge Expanders and Fan-out Expanders provide switching for connecting multiple targets to a host connection. Edge expanders support up to 128 SAS PHYs. Similarly, “Edge Expander Device Sets” can be constructed from multiple edge expanders. Direct connections, subtractive connections, and limited table routing enable communication between individual expanders (see Figure 1). Because they employ limited table routing, edge expanders are targeted at low-cost designs with limited storage scalability requirements.