Cache Management, Buffer Segmentation | Maxtor 6800 guide

PRODUCTDESCRIPTION

Cache Management

Buffer Segmentation

The data buffer is organized into two segments: the data buffer and the micro controller scratch pad. The data buffer is dynamically allocated for read and write data depending on the commands received. A variable number of read and write buffers may exist at the same time.

Read-Ahead Mode

Normally, this mode is active. Following a read request, disk read-ahead begins on the first sector and continues sequentially until the allocated buffer is full. If a read request is received during the read-ahead operation, the buffer is examined to determine if the request is in the cache. If a cache hit occurs, read- ahead mode continues without interruption and the host transfer begins immediately.

Automatic Write Reallocation (AWR)

This feature is part of the write cache and reduces the risk of data loss during deferred write operations. If a disk error occurs during the disk write process, the disk task stops and the suspect sector is reallocated to a pool of alternate sectors located at the end of the drive. Following reallocation, the disk write task continues until it is complete.

Write Cache Stacking

Normally, this mode is active. Write cache mode accepts the host write data into the buffer until the buffer is full or the host transfer is complete. A command complete interrupt is generated at the end of the transfer.

A disk write task begins to store the host data to disk. Host write commands continue to be accepted and data transferred to the buffer until either the write command stack is full or the data buffer is full. The drive may reorder write commands to optimize drive throughput.

2 – 4

Image 14

Maxtor 6800 Cache Management, Buffer Segmentation, Read-Ahead Mode, Automatic Write Reallocation AWR, Write Cache Stacking

Contents

HA RD Drive Produc T MA Nual DiamondMax Before You Begin U T I O N Contents Product Specifications Handling and Installation AT Interface Description Host Software Interface Glossary Interface CommandsService and Support Figures Manual Organization IntroductionMaxtor Corporation Abbreviations Key Words Signal ConventionsConventions Numbering DiamondMax 6800 Key Features Product Description Product Features Functional / Interface Defect Management Zone DMZ On-the-Fly Hardware Error Correction Code ECCLogical Block Addressing Software ECC Correction Buffer Segmentation Read-Ahead ModeCache Management Automatic Write Reallocation AWR Major HDA Components Cylinder Limitation Subsystem ConfigurationJumper Location/Configuration Dual Drive Support Performance Specifications Product SpecificationsDrive Configuration Models and Capacities Physical Dimensions Parameter Standard Metric EPA Energy Star Compliance Power RequirementsPower Mode Definitions Environmental Limits Reliability Specifications Shock and Vibration Canadian Emissions Statement Safety Regulatory ComplianceRadiated Electromagnetic Field Emissions EMC Compliance Pre-formatted Drive Handling and InstallationHard Drive Handling Precautions Important Notice Unpacking and Inspection Multi-pack Shipping Container Repacking Physical InstallationRecommended Mounting Configuration System Requirements Handling PrecautionsTools for Installation Drive Identification Information General Requirements Hard Drive Identification Installing in a Device Bay Systems Using Cable SelectInstalling 5.25-inch Mounting Brackets and Rails Mounting Drive in System Attaching Interface and Power Cables Attaching System Cables Bios Cmos Parameters System SetupSetting the Bios Cmos Hard Drive Preparation System Hangs During Boot Pin Description Summary Interface ConnectorAT Interface Description PIN Name Signal Name Signal Description Pin Description Table Timing Parameters Mode PIO Timing DMA Timing Mode MIN MAX Ultra DMA Timing Sustained Ultra DMA Data In Burst Device Terminating an Ultra DMA Data In Burst Initiating an Ultra DMA Data Out Burst Device Pausing an Ultra DMA Data Out Burst Device Terminating an Ultra DMA Data Out Burst Host Software Interface Error RegisterFeatures Register Task File Registers Cylinder Number Registers Sector Count RegisterSector Number Register Device/Head Register Command Register Command Name Command Code Parameters Used SDH Summary Device Control Register Control Diagnostic RegistersAlternate Status Register Digital Input Register Interrupt Handling Reset and Interrupt HandlingReset Handling Interface Commands Set Feature Commands Read Verify Sectors Read CommandsRead Sectors Read DMA Read Multiple Write Sectors Write CommandsSet Multiple Mode Write Verify Sectors Write Multiple Write DMA Set Feature Commands Set Features Mode Power Mode Commands Sleep Mode Initialization Commands Identify Drive 15-8 = PIO data transfer mode = Write Cache enabled Initialize Drive Parameters Format Track Seek, Format and Diagnostic CommandsExecute Drive Diagnostic A.R.T. Command Set Execute S.M.A.R.T No Quibble Service Service and SupportService Policy Support Internet MaxFax ServiceCustomer Service Access Time Glossary Cylinder Zero Gigabyte GB Logical Block Addressing Read Gate Signal THIN-FILM Media