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USER RESPONSIBLE FOR VERIFYING VERSION AND COMPLETENESS
OEM FUNCTIONAL SPECIFICATION ULTRASTAR XP (DFHC) SSA MODELS 1.12/2.25 GB - 1.0" HIGH
The full benefit of out of order transfers in only achieved if OOTI is also set. Read data is transferred on the
interface in the same order as it was read from the media.
3.5 Skew
3.5.1 Cylinder to Cylinder Skew
Cylinder skew is the sum of the sectors required for physically moving the heads (csms), which is a function
of the formatted block length and recording density (notch #), and reassign allowance sectors (ras = 3) used
to maintain optimum performance over the normal life of the drive.
Note: The values in the Mode Page 3 'Cylinder Skew Factor' are notch specific non-synchronized spindle
mode values. The value for notch 1 is returned when the Active Notch is set to 0.
Table 8. Optimal Cylinder Skew for several block lengths
In order to increase the likelihood that equivalent LBA's on two or more devices are located at the same
relative physical position when the devices are used in a synchronized spindle mode, cylinder skew is calcu-
lated differently. The cylinder skew calculations do not take into account known defective sites. To prohibit
revolutions from being missed on cylinder crossings by drives formatted while in a synchronized spindle
mode, an extra allowance for 6 defects is added that is not added when optimally formatted in a non-
synchronized mode.
3.5.2 Track to Track Skew
Note: The values in the SCSI Mode Page 3 'Track Skew Factor' are notch specific values. The value for
notch 1 is returned when the Active Notch is set to 0.
Notch #
User bytes / logical
block
1 2 3 4 5 6 7 8 9 10
256 42 42 42 40 38 36 36 36 36 32
512 28 28 27 26 25 24 24 23 22 21
520 26 26 26 26 24 24 23 22 22 21
522 26 26 26 25 24 24 23 22 22 20
524 26 26 26 25 24 24 23 22 22 20
528 26 26 26 25 24 24 23 22 22 20
600 24 24 24 23 22 22 21 20 20 20
688 22 22 22 21 20 20 20 20 18 18
744 21 21 21 20 20 20 18 18 17 17
Note: Contact an IBM Customer Representative for values at other formatted block lengths.
Source filename=PERFORMIBM CorporationPage 46 of 87