SATA Protocol Training August 28, 29, 2006

Agenda SATA Introduction 30 minutes Steve SATA Protocol 100 minutes Eric Layer Architecture Link Layer Physical Layer Phy Layer Frames and the Transport Layer SATA II Bus Doctor SATA Analyzer Demo 30 minutes Eric Q&As 20 minutes

Introduction August 28, 29, 2006

Before SAS/SATA Early 2000 and there are two main non-networked storage drive standards (i.e. Fibre Channel) ATA/IDE The most pervasive storage standard in the world (desktop or enterprise) Renamed to PATA after the introduction of SATA 18” internal cabling Host controls a master and slave drive SCSI HBA controls up to 15 drives Used on high-performance workstations, servers, and high-end peripherals; and RAID arrays U320 is the end of the road for this parallel interface Host Bus Adapter (HBA) utilizing DMA for maximum I/O Fibre Channel, ATAPI and SAS have their roots and legacy in SCSI

History of Parallel ATA Generation Standard Year Speed Key features IDE 1986 Pre-standard ATA 1994 PIO modes 0-2, multiword DMA 0 EIDE ATA-2 1996 16 MB/sec PIO modes 3-4, multiword DMA modes 1-2, LBAs ATA-3 1997 SMART ATA/ATAPI-4 1998 33 MB/sec Ultra DMA modes 0- 2, CRC, overlap, queuing, 80-wire Ultra DMA 66 ATA/ATAPI-5 2000 66 MB/sec Ultra DMA mode 3-4 Ultra DMA 100 ATA/ATAPI-6 2002 100 MB/sec Ultra DMA mode 5, 48-bit LBA Ultra DMA 133 ATA/ATAPI-7 2003 133 MB/sec Ultra DMA mode 6

Where ATA Resides in the PC Architecture CD HD SATA

Limitations of Parallel ATA Bandwidth limited to 133 MB/s Cyclic Redundancy Checking (CRC) for data but not commands Support attachment of 2 devices per cable Small switch or jumper for drive selection High pin count on signaling interface adds cost to cables, connectors and components Wide cables are cumbersome and inhibit airflow making cooling more difficult and expensive Connectors hard to insert and remove Prone to bent pins

Benefits of Serial Based Storage Frame-based transaction protocol (OSI model) Small, inexpensive connectors and cables Legacy support - ATA stack in SATA Ease of integration – cabling, jumpers Point-to-point connections (expanders, port multipliers) Pathway to higher data rates; 6 Gb/s is on the roadmap Improve bandwidth Wide ports permit several simultaneous connections, allowing for link aggregation (SAS) Lower cost Hot-plugable Enclosure management Interoperability with SAS Higher Performance Ease of integration – cabling, jumpers Pathway to higher speeds Legacy support for P-ATA drivers Lower cost eSATA; direct storage connect to host (e.g. no USB middleman)

PATA and SATA Comparisons Source: SATA Working Group

Native Command Queuing History of serial ATA Generation Standard Year Speed Key features Serial ATA ATA/ATAPI-7 2002 150 MB/sec Serial ATA II ATA/ATAPI-8 2005 300 MB/sec Native Command Queuing Serial ATA III ATA/ATAPI-9? ? 600 MB/sec

SATA Technology Today SATA has been the most successful recent new storage interface It has been a multi billion dollar market for several years In 2006 over 300 million hard disk drives will have SATA interfaces 400 Million Shipped in 2005 (source: Gartner) Market Leader – Seagate 40% share SATA has also made its appearance in solid state disks, DVD drives and tape drives In Desktop, notebooks, Consumer Products - DVR In the Enterprise! (thanks to STP) Challenges SAS in the enterprise Non-critical data Near-line and offline storage FC, SAS, and SATA will co-exist offering consumers with a choice of flexible storage options at varying price-points

SATA Layer Architecture August 28, 29, 2006

SATA Layer Architecture

SATA Layer Architecture

SATA Link Layer August 28, 29, 2006

Link Layer – Summary of Functions Sending/Receiving Frames 8b/10b encoding Scrambling/Unscrambling Flow control CRC calculation

Link Layer - 8b/10b Encoding Data transferred across the link must first be converted from 8-bit values (bytes) into 10 bit values (symbols) Process is called 8b/10b encoding Invented by IBM Also used in the following protocols: Ethernet, Fibre Channel Purpose for encoding Clock insertion and recovery Creates sufficient transition density to limit “Run Length” DC Balance – main “equal” number of 1’s and 0’s Ability to encode for special control characters (K)

Link Layer - 8b/10b Encoding Two encodings for each 8-bit value Dependence on the current running disparity Two lookup tables are provided for in the specifications

Link Layer – Scrambling/Descrambling SATA frames are scrambled to help with EMI (primitives are not scrambled) Scrambling occurs before 8b/10b “Seeding” resets at the detection of a SOF Descrambled on receive side after the 8b/10b

SATA Primitives Primitives are used as semaphores. They are fixed in content and meaning Primitive is a dword with one control character followed by 3 data characters Primitives are used in SATA – the equivalent in Fibre Channel is ordered set First character is K28.3 (for SATA primitives), or K28.6 (special SATA error primitive) SATA primitives always send the control character first on the wire ALIGN K28.5 D10.2 D10.2 D27.3 first second third fourth

SATA Primitives SOF D23.1 D23.1 D21.5 K28.3 The Align primitives establish dword boundaries within the serial bit stream. They are sent as data during OOB, and every 2048 dwords there after Sent First SOF 3 2 1 0 D23.1 D23.1 D21.5 K28.3

SATA Primitives 18 primitives defined ALIGN CONT R_ERR DMAT R_IP EOF HOLD HOLDA PMACK PMNAK PMREQ_P PMREQ_S R_ERR R_IP R_OK R_RDY SOF SYNC WTRM X_RDY

SATA Primitives Primitives are used in a variety of circumstances including: Indicating intent to send an FIS Indicating beginning and end of each FIS Flow Control signaling in response to Transport Layer Buffer state Reporting Transmission Status

Physical Layer August 28, 29, 2006

Physical Layer - Summary Defines the connectors and cabling used to transmit and receive SATA signaling and data information

Physical Layer - SATA Device Connector Appearance of Serial ATA Connectors (Drawing courtesy of Molex) Device connector sizes and locations Serial Device plug connector 2.5" power signal Serial ATA signal connector (pin S1) Serial 3.5” Serial ATA power connector (pin P1) power signal Legacy Power (vendor specific) (5.25” form factor also defined for devices like tape drives and DVDs) in comparison… Parallel 3.5” Host receptacle connector parallel ATA signals 4-pin power Graphics courtesy of the SCSI Trade Association and HP

Physical Layer - SATA Cabling SATA to SATA (1), CO, ST The most common internal for SATA (and SAS); 1 meter maximum length SATA Power To provide legacy power support eSATA Power (2m) External SATA; designed for use with external storage products; bypasses the USB route Graphics courtesy of Molex

Phy Layer August 28, 29, 2006

Physical Layer - Summary OOB (Out of Band) Signaling Speed Negotiations Byte/dword synchronization

Phy Layer - (OOB) Most primitive level of communication is OOB They are pattern of idle times and burst times, distinguished by length of time between idles Idle time (and negation time) are when there are voltage levels Also known as DC idle Burst time is during the transmission of the ALIGN primitives Since byte sync has not occurred yet, the actual bits sent are not relevant – 40 bits will always been detected and consider an ALIGN

Phy Layer - (OOB) COMINIT/COMRESET and COMWAKE are bursts of 6 ALIGN (0) separated by IDLEs Length of the idle time determines the type of OOB signal Senders sends 6 – receiver only need to detect 4 (per spec) COMRESET are sent by hosts COMINIT are sent by devices OOB Signal Idle Time Negation Time COMWAKE 55 to 175 ns > 175 ns COMINIT/COMRESET 175 to 525 ns > 525 ns

Phy Layer - OOB COMWAKE

Phy Layer - OOB COMINIT/COMRESET Electrically, COMINIT and COMRESET appear exactly the same, the only difference is the direction in which the ALIGN patterns are being sent. Host to device: COMRESET; device to host: COMINIT

SATA Power-On Initialization Starts with the assertion of hardware reset Begins Out-Of-Band (OOB) signaling Allows host and device to initialize link communications Ends with successful transmission of ALIGN primitives Then speed negotiations

Power-On Initialization Process Host Device The register FIS delivers the power-on signature, indicating whether the device is ATA, ATAPI, SEMB, Port Multiplier, etc.

SATA Power-On Initialization

Error Situation Example: Host and Device are unable to establish a connection. Continuous transmission errors are seen from both the Host and Device. No COMINITs present. Indicates problem with Device connection

Primitive Handshaking Sender Receiver X_RDY R_RDY SOF Frame . EOF R_IP WTRM R_OK

Primitive Handshaking Example: Host sends commands but commands are not completed Trace indicates that Host is not properly handling primitive handshaking and is not receiving frames

SATA Speed Negotiation Fast to slow progression SATA target device sends ALIGN primitives at the fastest supported rate Waits for host to reply with ALIGNs If no reply after sending 2048 (i.e., the host doesn’t support this speed), step down to next slower speed and try again

SATA Speed Negotiation When host replies with ALIGNs, it has locked at the current frequency and negotiation is complete Speed Negotiation

Frames August 28, 29, 2006

Frames and the Transport Layer Frames operate at the Transport Layer Primitives operate at the Link Layer Frames convey variable content. A frame starts with a Start of Frame primitive (SOF). The frame ends with a CRC dword and an End of Frame primitive (EOF). In between the two primitives are dwords that make up the information content

Frames and the Transport Layer FIS 27 – Used to issue ATA commands to the Device FIS 46 – Used to transmit Data FIS 34 – Used by the Device to indicate command completion status FIS 39 - Used by the device to indicate that it is ready for a DMA transfer FIS 5F – Used by the device to set up a PIO transfer

Example: Transaction is not completed Frames Example: Transaction is not completed Trace indicates invalid CRC. R_ERR indicates receiver detected invalid frame.

From PATA to SATA August 28, 29, 2006

PATA to SATA Task File In the ATA device In parallel ATA, accesses to these registers result in parallel ATA traffic In serial ATA, a Shadow Task file register bank is managed by the host (mirrors the ATA device’s task file) Allows accesses to these registers to be grouped into larger, more efficient serial transfers

PATA to SATA ATA host ATA device PCI bus Parallel ATA Task file Pass-thru Task file IO Reads/Writes SATA host SATA device Serial ATA Shadow task file Task file PCI bus Frame Information Structures

SATA II August 28, 29, 2006

SATA II Native Command Queuing Port Selector Port Multiplier

Native Command Queuing For multiple outstanding commands in device Supports reordering of commands (by device! not host) Supports out-of-order data delivery and re-assembly SCSI tagged command queuing Performance of 7200 rpm drive with NCQ is equivalent to that of a standard 10k rpm drive Less wear-and-tear on drives Supported through the FPDMA Read Command and FPDMA Write Command 25% Boost In Performance

Port Selector SATA typically operates point to point Port selector permits 1 device to communicate with 2 hosts Host 1 Link Drive Host 2

Port Multiplier SATA typically operates point to point Port multiplier feature permits for one SATA link to connect to many devices Active host with a ratio of 1 host to a maximum of 15 devices – it is acting very much like a hub or repeater 1 to … Single SATA Link 16 SATA drives

Q&A August 28, 29, 2006

Thank You August 28, 29, 2006