7K6000 datasheet(21/274 Pages) WESTERN

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HGST Hard Disk Drive Specification

4.4

Drive organization

4.4.1

Drive Format

Upon shipment from HGST Japan manufacturing the drive satisfies the sector continuity in the physical format by

means of the defect flagging strategy described in Section 5 on page 25 in order to provide the maximum

performance to users.

4.4.2

Cylinder allocation

Physical cylinder is calculated from the starting data track of 0. It is not relevant to logical CHS. Depending on the

capacity some of the inner zone cylinders are not allocated.

Data cylinder

This cylinder contains the user data which can be sent and retrieved via read/write commands and a spare area for

reassigned data.

Spare cylinder

The spare cylinder is used by HGST Japan manufacturing and includes data sent from a defect location.

4.5

Performance characteristics

Drive performance is characterized by the following parameters:

 Command overhead

 Mechanical positioning

- Seek time

- Latency

 Data transfer speed

 Buffering operation (Look ahead/Write cache)

All the above parameters contribute to drive performance. There are other parameters that contribute to the

performance of the actual system. This specification defines the characteristics of the drive, not the characteristics

of the system throughput which depends on the system and the application.

4.5.1 Command overhead

Command overhead is defined as the time required

 from the time H->D Reg FIS w/ command bit is sent by host

 to the time

 PIO Set Up FIS is sent by device(PIO Read/Write)

 DATA FIS is sent by device(DMA Read)

 DMA Activate FIS is sent by device(DMA Write)

 DMA Set Up FIS is sent by device(NCQ Read/Write)

 Seek Start (Read cache not hit or Seek)

The table below gives average command overhead.

Command type

(Drive is in quiescent state)

Typical time (ms)

Typical time for NCQ

command (ms)

Read (Cache not hit)

0.2

Read (Cache hit)

0.2

Write

0.5

Seek

0.5

not applicable

Table 6

Command overhead

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