Quantum FIREBALL PLUS AS 10.2 User Manual

Basic Principles of Operation
5-13 Quantum Fireball Plus AS 10.2/20.5/30.0/40.0/60.0 GB AT
5.3.2.4
5.3.2.45.3.2.4
5.3.2.4 Skew Offsets
Skew OffsetsSkew Offsets
Skew Offsets
Table 5-2
Table 5-2 Table 5-2
Table 5-2 Skew Offsets
Note:
Note:Note:
Note: Nominal wedge-to-wedge time of 56.25 ms is used. Worst case
instantaneous spindle variation (±0.12%) is used while calcu-
lating to provide a safety margin.
Wedge offsets are rounded to the closest whole number.
5.3.2.5
5.3.2.55.3.2.5
5.3.2.5 Runtime Calculation
Runtime CalculationRuntime Calculation
Runtime Calculation
Since the wedge-to-wedge time is constant over the entire disk, a single set of head
and cylinder skew offsets will fulfill the requirement for all recording zones. The
formula used to compute the wedge skew for a given cylinder and head is:
Wedge skew = [C* ((# of heads – 1) * TS + CS) + H * TS] MOD 148
Where:C = Cylinder number
H = Head number
TS = Head Skew Offset
CS Cylinder Skew Offset
(wedges/track = 148)
5.3.3
5.3.35.3.3
5.3.3 Error Detection and Correction
Error Detection and CorrectionError Detection and Correction
Error Detection and Correction
As disk drive areal densities increase, obtaining extremely low error rates requires
a new generation of sophisticated error correction codes. Quantum Fireball Plus AS
hard disk drive series implement 320-bit Reed-Solomon error correction techniques
to reduce the uncorrectable read block error rate to less than one bit in 1 x 10
14
bits
read.
When errors occur, an automatic retry of 15 10-bit symbols and a more rigorous 16
10-bit symbols correction algorithm enable the correction of any sector with single
bursts, or up to sixteen multiple random one 10-bit symbol burst. In addition to
these advanced error correction capabilities, the drive uses an additional cross-
checking code and algorithm to double check the main ECC correction. This greatly
reduces the probability of a miscorrection.
5.3.3.1
5.3.3.15.3.3.1
5.3.3.1 Background Information on Error Correction Code and ECC On-the-Fly
Background Information on Error Correction Code and ECC On-the-FlyBackground Information on Error Correction Code and ECC On-the-Fly
Background Information on Error Correction Code and ECC On-the-Fly
A sector on the Quantum Fireball Plus AS AT drive is comprised of 512 bytes of
user data, followed by four cross-checking (XC) bytes (32 bits), followed by 40 ECC
check bytes (320 bits) or 32 10-bit symbols. The four cross-checking bytes are used
to double check the main ECC correction and reduce the probability of
miscorrection. Errors of up to 150 bits within one sector can be corrected “on-the-
fly,” in real time as they occur, allowing a high degree of data integrity with no
impact on the drive’s performance.
SWITCH TIME
SWITCH TIMESWITCH TIME
SWITCH TIME WEDGE OFFSET
WEDGE OFFSETWEDGE OFFSET
WEDGE OFFSET
Head Skew 1.75 ms 31
Cylinder Skew 1.20 ms 21

Quantum FIREBALL PLUS AS 10.2 Specifications

General

Brand	Quantum
Model	FIREBALL PLUS AS 10.2
Category	Storage
Language	English