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7.6Deferred Auto-Reallocation
Deferred Auto-Reallocation (DAR) simplifies reallocation algorithms at the system level by allowing the drive to reallocate unreadable locations on a subsequent write command. Sites are marked for DAR during read oper- ations performed by the drive. When a write command is received for an LBA marked for DAR, the auto-reallo- cation process is invoked and attempts to rewrite the data to the original location. If a verification of this rewrite fails, the sector is re-mapped to a spare location.
This is in contrast to the system having to use the Reassign Command to reassign a location that was unread- able and then generate a write command to rewrite the data. DAR is most effective when AWRE and ARRE are enabled—this is the default setting from the Seagate factory. With AWRE and ARRE disabled DAR is unable to reallocate the failing location and will report an error sense code indicating that a write command is being attempted to a previously failing location.
7.7Idle Read After Write
Idle Read After Write (IRAW) utilizes idle time to verify the integrity of recently written data. During idle periods, no active system requests, the drive reads recently written data from the media and compares it to valid write command data resident in the drives data buffer. Any sectors that fail the comparison result in the invocation of a rewrite and auto-reallocation process. The process attempts to rewrite the data to the original location. If a verification of this rewrite fails, the sector is re-mapped to a spare location.
36 | Cheetah NS SAS Product Manual, Rev. B |
Cheetah NS SAS
ST3400755SS
Page
Contents
Seagate Technology support services
Defect and error management
Installation
Interface requirements
List of Figures
Typical ST3400755SS drive +5V and +12V current profiles
Cheetah NS SAS Product Manual, Rev. B
Scope
Cheetah NS SAS Product Manual, Rev. B
Electromagnetic compatibility
Standards, compliance and reference documents
Standards
Electromagnetic susceptibility
Compliance
Reference documents
Cheetah NS SAS Product Manual, Rev. B
General description
Performance
Standard features
Media description
Reliability
Programmable drive capacity
Factory-installed options
Formatted capacities
ST3400755SS
Cheetah NS SAS Product Manual, Rev. B
Access time
Performance characteristics
Internal drive characteristics
Seek performance
Format command execution time minutes
General performance characteristics
Start/stop time
Prefetch/multi-segmented cache control
Cache operation
Caching write data
Prefetch operation
Recoverable Errors
Reliability specifications
Error rates
Unrecoverable Errors
Interface errors
Reliability and service
Seek errors
Preventive maintenance
Performance impact
4 S.M.A.R.T
Controlling S.M.A.R.T
Reporting control
Temperature Log Page 0Dh
Predictive failures
Thermal monitor
Implementation
State of the drive prior to testing
DST failure definition
Invoking DST
Extended test Function Code 010b
Product warranty
Short test Function Code 001b
Log page entries
Shipping
Product repair and return information
Cheetah NS SAS Product Manual, Rev. B
DC power requirements
Physical/electrical specifications
AC power requirements
ST3400755SS DC power requirements
Conducted noise immunity
General DC power requirement notes
Power sequencing
Current profiles
Power dissipation
Typical ST3400755SS drive +5V and +12V current profiles
Temperature
Environmental limits
Shock and vibration
Relative humidity
Effective altitude sea level
Shock
Package size Packaged/product weight Drop height
Recommended mounting
Acoustics
Air cleanliness
Vibration
Corrosive environment
X表示该部件(于同类物品程度上)所含的危险和有毒物质中国RoHS MCV标准所定义的门槛值。
China Restriction of Hazardous Substances RoHS Directive
Mechanical specifications
Physical dimensions
Cheetah NS SAS Product Manual, Rev. B
Defect and error management
Drive internal defects/errors
Drive error recovery procedures
77.87
SAS system errors
Background Media Scan
Media Pre-Scan
Deferred Auto-Reallocation
Idle Read After Write
Installation
Drive orientation
Cooling
Air flow
Drive mounting
Grounding
Cheetah NS SAS Product Manual, Rev. B
SAS features
Interface requirements
Dual port support
Scsi commands supported
Commands supported by Cheetah NS SAS family drives
Command name Command code Supported
Commands supported by Cheetah NS SAS family drives
Commands supported by Cheetah NS SAS family drives
Commands supported by Cheetah NS SAS family drives
Mode Sense data
Inquiry data
Cheetah NS SAS inquiry data Bytes Data hex
Page
2.1 ST3400755SS Mode Sense data
Mode Pages
Supported Feature or condition
Miscellaneous operating features and conditions
Miscellaneous features
Miscellaneous status
SAS physical interface
Datum B
Physical characteristics
Connector requirements
Pin descriptions
Pin Signal name Signal type
Electrical description
SAS pin descriptions
SAS transmitters and receivers
Signal characteristics
Power
Ready LED Out
General interface characteristics
LED drive signal
Differential signals
Eye masks Eye masks overview
Absolute amplitude
Receive eye mask
Jitter tolerance masks
Normalized time in UI
Jitter
Peak-to
Sinusoidal
Frequency in kHz
Transmitter signal characteristics
Signal characteristica Units Gbps
Maximum allowable jitter
Receiver signal characteristics
Signal characteristic Units Gbps
Gbps m, n Deterministic jitterq
Compliant jitter test pattern Cjtpat
Impedance specifications
Receiver jitter tolerance
Impedance requirements Sheet 1
Transmitter characteristics
Impedance requirements Sheet 2
Electrical TxRx connections
= -5,437dB
Shows the zero-length test load
Receiver characteristics
Cheetah NS SAS Product Manual, Rev. B
Presales Support
Seagate Technology support services
Internet
Technical Support
Warranty Service
Data Recovery Services Authorized Service Centers
Data Recovery Services Call Center Toll-free Direct dial
Index
Numerics
Page
SAS
See also cooling