SAS - Serial Attached SCSI Hard Drive Overview

There's a new hard drive interface / format in town. It's called Serial Attached SCSI (typically abbreviated to SAS). It shares the same connector type as SATA hard drives, but uses the build quality of SCSI hard drives to acheive the performance and reliability we've come to expect from enterprise class disk drives.

Features of SAS Hard Drives	Benefits
3.0 Gb/sec transfer rate	Sets new standards for enterprise-class performance, 2nd generation on track for 6.0 Gb/sec throughput
Point-to-point architecture	Ensures maximum bandwidth by providing dedicated signal path for each device, eliminates daisy-chain slowdowns and address conflicts
Full-duplex operation	Doubles effective throughput by enabling signal path to handle data transfers in both directions at once
Advanced command queuing	Maintains high performance under demanding enterprise traffic conditions (e.g., frequent, concurrent access by multiple initiators or host)
Utilizes existing SCSI command sets	Preserves investment in legacy software and drivers, eases migration path (no need for system-level workarounds required for ATA)
Edge and fan-out expanders	Routing devices ensure seamless scalability, enable aggregation of up to 16,384 devices while preserving performance
Available in small form factor (2.5-inch drive) Fall 2004	Allows greater drive count in dense computing environments (e.g., crowded data centers) for higher throughput (IOPS/U), reduces power consumption
Backplanes and HBAs compatible with SATA	Connectivity for multiple device types lowers TCO, gives flexibility to specify best drive for intended use: SAS for transactional/online performance and reliability, Serial ATA for nearline and backup/restore storage
Compact cabling and connectors	Simplified cable routing, saves space and improves airflow/cooling in system cabinets, connectors easily fit on small form factor devices
Hot plug, blind mate connections	Add/remove drives without system shutdown, facilitates connection in cramped or inaccessible installations