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Seagate ST300MP0004 Savvio 15K.1 FC User Guide - Page 48

Idle Read After Write

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7.7 Idle 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. 40 Savvio 15K.1 FC Product Manual, Rev. B

Section	Page
1.0 Scope	9
2.0 Applicable standards and reference documentation	11
2.1 Standards	11
2.1.1 Electromagnetic compatibility	11
2.1.1.1 Electromagnetic susceptibility	11
2.1.2 Electromagnetic compliance	12
2.2 European Union Restriction of Hazardous Substances (RoHS)	12
2.3 Reference documents	13
3.0 General description	15
3.1 Standard features	16
3.2 Media description	17
3.3 Performance	17
3.4 Reliability	17
3.5 Formatted capacities	17
3.5.1 Programmable drive capacity	18
3.6 Factory-installed accessories	18
3.7 Options	18
4.0 Performance characteristics	19
4.1 Internal drive characteristics	19
4.2 Seek performance characteristics	19
4.2.1 Access time	19
4.2.2 Format command execution time	20
4.2.3 General performance characteristics	20
4.3 Start/stop time	20
4.4 Prefetch/multi-segmented cache control	21
4.5 Cache operation	21
4.5.1 Caching write data	21
4.5.2 Prefetch operation	22
5.0 Reliability specifications	23
5.1 Error rates	23
5.1.1 Recoverable Errors	23
5.1.2 Unrecoverable Errors	24
5.1.3 Seek errors	24
5.1.4 Interface errors	24
5.2 Reliability and service	24
5.2.1 Annualized Failure Rate (AFR) and Mean Time Between Failure (MTBF)	24
5.2.2 Preventive maintenance	24
5.2.3 Hot plugging the drive	25
5.2.4 S.M.A.R.T.	25
5.2.5 Thermal monitor	26
5.2.6 Drive Self Test (DST)	27
5.2.6.1 DST failure definition	27
5.2.6.2 Implementation	28
5.2.6.2.1 State of the drive prior to testing	28
5.2.6.2.2 Invoking DST	28
5.2.6.2.3 Short and extended tests	28
5.2.6.2.4 Log page entries	29
5.2.6.2.5 Abort	29
5.2.7 Product warranty	29
6.0 Physical/electrical specifications	31
6.1 AC power requirements	31
6.2 DC power requirements	31
6.2.1 Conducted noise immunity	33
6.2.2 Power sequencing	33
6.2.3 Current profiles	33
6.3 Power dissipation	35
6.4 Environmental limits	38
6.4.1 Temperature	38
6.4.2 Relative humidity	39
6.4.3 Effective altitude (sea level)	39
6.4.4 Shock and vibration	39
6.4.4.1 Shock	39
6.4.4.2 Vibration	42
6.4.5 Air cleanliness	42
6.4.6 Corrosive environment	42
6.4.7 Acoustics	43
6.4.8 Electromagnetic susceptibility	43
6.5 Mechanical specifications	44
7.0 Defect and error management	45
7.1 Drive internal defects/errors	45
7.2 Drive error recovery procedures	45
7.3 FC-AL system errors	46
7.4 Background Media Scan	47
7.5 Media Pre-Scan	47
7.6 Deferred Auto-Reallocation	47
7.7 Idle Read After Write	48
8.0 Installation	49
8.1 Drive orientation	49
8.2 Cooling	49
8.3 Drive mounting	50
8.4 Grounding	50
9.0 Interface requirements	51
9.1 FC-AL features	51
9.1.1 Fibre Channel link service frames	51
9.1.2 Fibre Channel task management functions	52
9.1.3 Fibre Channel task management responses	52
9.1.4 Fibre Channel port login	53
9.1.5 Fibre Channel port login accept	54
9.1.6 Fibre Channel Process Login	54
9.1.7 Fibre Channel Process Login Accept	55
9.1.8 Fibre Channel fabric login	55
9.1.9 Fibre Channel fabric accept login	56
9.1.10 Fibre Channel Arbitrated Loop options	57
9.2 Dual port support	57
9.3 SCSI commands supported	58
9.3.1 Inquiry data	63
9.4 Miscellaneous operating features and conditions	64
9.5 FC-AL physical interface	65
9.5.1 Physical characteristics	65
9.5.1.1 Physical description	65
9.5.2 Connector requirements	66
9.5.3 Electrical description	66
9.5.4 Pin descriptions	67
9.5.5 FC-AL transmitters and receivers	68
9.5.6 Power	68
9.5.7 Fault LED Out	68
9.5.8 Active LED Out	69
9.5.9 Enable port bypass signals	69
9.5.10 Motor start controls	69
9.5.11 SEL_6 through SEL_0 ID lines	70
9.5.11.1 Parallel Enclosure Services Interface (ESI)	70
9.5.12 Device control codes	72
9.6 Signal characteristics	72
9.6.1 TTL input characteristics	72
9.6.2 Differential PECL output	73
9.6.3 Differential PECL input	73

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Savvio 15K.1 FC Product Manual, Rev. B

7.7

Idle 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.