August 28, 29, 2006

SATA Protocol Training

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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 Demo30 minutes Eric

Q&As 20 minutes

August 28, 29, 2006

Introduction

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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

SCSIHBA 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

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History of Parallel ATA

Generation Standard Year Speed Key featuresIDE 1986 Pre-standard

ATA 1994 PIO modes 0-2, multiword DMA 0

EIDE ATA-2 1996 16 MB/secPIO modes 3-4,

multiword DMA modes 1-2, LBAs

ATA-3 1997 16 MB/sec SMART

ATA/ATAPI-4 1998 33 MB/secUltra DMA modes 0- 2, CRC, overlap, queuing,

80-wireUltra DMA

66ATA/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

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Where ATA Resides in the PC Architecture

CD

HD

SATA

SATA

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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

Limitations of Parallel ATA

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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

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PATA and SATA Comparisons

Source: SATA Working Group

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History of serial ATA

Generation Standard Year Speed Key featuresSerial 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

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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 - DVRIn 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

August 28, 29, 2006

SATA Layer Architecture

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SATA Layer Architecture

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SATA Layer Architecture

August 28, 29, 2006

SATA Link Layer

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Link Layer – Summary of Functions

Sending/Receiving Frames

8b/10b encoding

Scrambling/Unscrambling

Flow control

CRC calculation

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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)

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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

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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

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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

first second third fourth

ALIGN K28.5 D10.2 D10.2 D27.3

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SATA Primitives

The Align primitives establish dword boundaries within the serial bit stream. They are sent as data during OOB, and every 2048 dwords there after

D23.1 D23.1 D21.5 K28.3 3 2 1 0

Sent First

SOF

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SATA Primitives

18 primitives defined ALIGN CONT DMAT EOF HOLD HOLDA PMACK PMNAK PMREQ_P PMREQ_S

R_ERR R_IP R_OK R_RDY SOF SYNC WTRM X_RDY

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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

August 28, 29, 2006

Physical Layer

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Physical Layer - Summary

Defines the connectors and cabling used to transmit and receive SATA signaling and data information

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Physical Layer - SATA Device Connector

Serial ATA signal connector(pin S1)

Appearance of Serial ATA Connectors(Drawing courtesy of Molex)

parallel ATA signals 4-pin power

3.5”Parallel

power signal

2.5"

Serial

Device connector sizes and locations

Device plugconnector

Host receptacleconnector

power signal

3.5”Serial

Legacy Power(vendor specific)

Serial ATA power connector(pin P1)

(5.25” form factor also defined for devices like tape drives and DVDs)in comparison…

Graphics courtesy of the SCSI Trade Association and HP

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Physical Layer - SATA Cabling

Graphics courtesy of Molex

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

August 28, 29, 2006

Phy Layer

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Physical Layer - Summary

OOB (Out of Band) Signaling

Speed Negotiations

Byte/dword synchronization

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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

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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

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Phy Layer - OOB COMWAKE

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Phy Layer - OOB COMINIT/COMRESETElectrically, 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

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SATA Power-On Initialization

Starts with the assertion of hardware resetBegins Out-Of-Band (OOB) signalingAllows host and device to initialize link communicationsEnds with successful transmission of ALIGN primitivesThen speed negotiations

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Power-On Initialization ProcessHost Device

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SATA Power-On Initialization

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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

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Primitive Handshaking

Sender ReceiverX_RDY

R_RDY

SOFFrame

.

.

.EOF

R_IP

R_OK

WTRM

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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

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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

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SATA Speed Negotiation

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

Speed Negotiation

August 28, 29, 2006

Frames

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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

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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

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Frames

Example: Transaction is not completed

Trace indicates invalid CRC. R_ERR indicates receiver detected invalid frame.

August 28, 29, 2006

From PATA to SATA

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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

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PATA to SATA

Task filePCI bus Parallel ATAPass-

thru

ATA device

ATA host

Task filePCI busSerial ATAShado

w task file

SATA device

SATA host

IO Reads/Writes

Frame InformationStructures

August 28, 29, 2006

SATA II

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SATA II

Native Command Queuing

Port Selector

Port Multiplier

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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

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Port Selector

SATA typically operates point to point

Port selector permits 1 device to communicate with 2 hosts

Link DriveHost 1

Host 2

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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

Single SATA Link1 to …

16 SATA drives

August 28, 29, 2006

Q&A

August 28, 29, 2006

Thank You