Course 325: Serial Attached SCSI (SAS) Fundamentals

Serial Attached SCSI is the logical evolution of SCSI, including its long-established software advantage and the Serial ATA electrical and physical connection interface. With enterprise storage requirements escalating and becoming more complex, factors such as larger capacity, greater density, security, scalability and accessibility are more critical than ever.

This course explores why industry in defining a new serial point-to-point enterprise device attach interface, leveraging the SCSI protocol set and supporting a wide range of price/performance storage.

Technology choice in the future

• Overview of SCSI
• SCSI future beyond U640
• Serial ATA new markets
• Fibre Channel devices
• 1394a and 1394b
• USB 2.0
• Serial Attached SCSI is the logical evolution of SCSI

Serial Attached SCSI

• Limits of Serial ATA
• SAS and SATA
• Why is Serial Attached SCSI?
• End user benefits of Serial Attached SCSI
• The Benefits
• Role of T10 Committee
• Serial Attached SCSI overview
• Serial Attached SCSI environment
• Market Trends
• Serial Attached SCSI products

SAS Overview

• Why Serial Attached SCSI?
• Why is the new standard necessary?
• Protocols Serial Attached SCSI (SAS) interconnect
• Transport protocols that use the SAS interconnect:
• Serial SCSI Protocol (SSP)
• Serial ATA Tunneled Protocol (STP)
• Serial Management Protocol (SMP)
• Initiators and Targets
• Expander Device Topologies
• Links (Physical vs. Logical)
• Ports (1x and 4x)
• Physical Layer
• Link Layer
• Transport Layer
• Logical Operation Overview

SAS architecture

• Architecture
• Physical links and phys
• Ports (narrow ports and wide ports)
• SAS devices
• Expander devices (edge expander devices and fanout expander devices)
• Service delivery subsystem
• Domains
• Expander device topologies
• Edge expander device set
• Maximum expander device set topology
• Fanout expander device topology
• Pathways
• Connections

SAS domains

• Service delivery subsystem with expander devices
• SSP initiator port(s)
• SSP target port (s)
• STP initiator port(s)
• STP target port (s)
• SMP initiator port(s)
• SMP target port (s)
• SAS domain bridging to ATA domains

SAS Names and identifiers overview

• SAS addresses
• Hashed SAS address
• Device names
• Port names
• Port identifiers
• Phy identifiers
• State machines
• Resets
• Expander device model

Physical Layer

• Physical layer overview
• Physical Layer Functions
• Passive interconnect
• Connectors
• Cables
• SAS internal cables
• SAS external cables
• Backplanes
• Single and Dual ports
• 1x and 4x wide
• Transmitter and receiver electrical characteristics
• Characteristics at IT, CT, and XT
• Jitter
• Receiver jitter tolerance
• Compliant jitter test pattern (CJTPAT)
• Impedance
• Electrical TxRx connections
• Transmitter characteristics
• Receiver
• Spread spectrum clocking
• Non-tracking clock architecture
• READY LED signal electrical characteristics

Phy layer

• Phy layer overview
• Encoding (8b10b)
• Character encoding and decoding
• Bit order
• Out of band (OOB) signals
• SP (phy layer) state machine
• SP_DWS (phy layer dword synchronization) state machine

Link Layer

• Link Layer functions
• 8b/10b encoding
• OOB
• Primitives
• Primitives not specific to type of connections
• Primitives used only inside SSP and SMP connections
• Primitives used only inside STP connections and on SATA physical links
• Address frames and usage
• Link initialization
• Power management
• Loopback tests
• Physical vs. logical links
• CRC and Scrambling
• Clock skew management
• Idle physical links
• Address frames
• Identification and hard reset sequence
• Identification and hard reset sequence overview
• Power management
• Closing an SSP connection
• SSP (link layer for SSP phys) state machines
• STP Link Layer
• SMP Link Layer
• SSP Connections
• STP Connections
• Error handling

Port layer

• Port layer overview
• PL (port layer) state machines
• Timers and count
• Port layer overall control (PL_OC) state machine
• Port layer phy manager (PL_PM) state machine

Transport Layer

• Transport Layer Functions
• SSP transport layer
• SSP frame format
• Information units
• Sequences of SSP frames
• SSP transport layer handling of link layer errors.
• SSP transport layer error handling
• STP transport layer
• SMP transport layer
• MT (transport layer for SMP ports) state machines

Application layer

• Application layer overview
• SCSI application layer
• Device server error handling
• SCSI transport protocol event notifications
• SCSI com 306
• SCSI mode parameters
• SCSI log parameters
• SCSI power conditions
• SCSI vital product data (VPD)
• ATA application layer
• Management application layer

State Machines

• Descriptions & Operations
• Transport & Link
• SMP Transport & Link
• SAS Link
• State machines and SAS device, SAS port, and SAS phy objects
• Messages between state machines
• Messages between phy layer and other layers
• Messages between link layer, port layer, and transport layer for SSP
• Messages between link layer, port layer, and transport layer for SMP
• Transport layer to application layer for SSP
• Transport layer to application layer for SMP

Expanders

• Overview
• Expander device model overview
• Expander ports
• Expander connection manager (ECM)
• Expander connection router (ECR)
• Broadcast primitive processor (BPP)
• Expander device interfaces
• Expander device routing
• Resets
• Power Management.
• STP Multi-initiator
• Expander communication
• Multiple expanders

Standards and Futture Trends

• Current Standards
• T10 Committee
• Serial ATA Group
• Serial Attached SCSI Working Group
• Products
• Future

Testing and verification (hands-on)

• The design of systems & devices
• Practical Verification of Embedded Hardware and Software
• Test and verification of SAS semiconductors, devices
• Systems design verification systems
• SAS Analyzers
• SAS traffic capture, display and analysis
• Collection of SAS trace data
• Hardware captures and displays SAS traffic between host and device
• Capture and decoding of the SAS protocol
• Sync generation or cable testing
• Detect errors
• Real Time Monitor
• Compatibility Tester
• Analyze protocol traffic and debug and test devices
• Test Cases and Scenarios
• Case Study 1
• Case Study 2
• Lab 1
• Lab 2
• Lab 3