Magnetic Disk Write Limit Setting via Bit Error Rate Modeling
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Solution Overview
Problem
Magnetic disk devices face challenges in accurately setting the upper limit of write times to prevent side erase due to adjacent track interference, which affects data integrity and requires a method to determine when data becomes unreadable to ensure reliable storage.
Innovation Solution
A method involving measuring bit error rates at different write times, deriving a function to approximate bit error rates, and setting the upper limit based on a threshold error rate to determine when data becomes unreadable, thereby preventing side erase and ensuring data correctness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the upper limit value of the number of write times is set to prevent side erase due to ATI, then data integrity is improved, but the processing time for determining the upper limit increases
Solution Approach 1:
The patent applies preliminary action by pre-determining the upper limit value of the number of write times through a systematic measurement and calculation process. The controller measures bit error rates at multiple predetermined number of write times, derives an approximate function, and calculates the upper limit value in advance before actual data writing operations begin. This allows the system to have the upper limit value ready for use, avoiding time-consuming calculations during operational phases.
Solution Approach 2:
The patent uses a simplified measurement approach where bit error rates are measured at a limited number of predetermined write times (e.g., 3-5 points) rather than continuously monitoring all possible write times. This discrete sampling method provides sufficient accuracy for determining the upper limit while significantly reducing the time and computational resources required compared to exhaustive measurement approaches.
2Productivity
If the upper limit value is set too high, then processing efficiency is improved, but side erase due to ATI occurs reducing data reliability
Solution Approach 1:
The patent implements feedback by using the measured bit error rates to derive an approximate function that relates the number of write times to error rates. The controller continuously monitors bit error rates at different write times, feeds this information back into the approximate function, and uses the function to determine the precise upper limit value where the bit error rate reaches a predetermined threshold. This feedback mechanism ensures the upper limit is set accurately to prevent side erase while maximizing processing efficiency.
Solution Approach 2:
The patent applies parameter changes by varying the number of write times to adjacent tracks and measuring the corresponding bit error rates in the recording area. By changing these parameters systematically and analyzing the relationship through an approximate function, the system identifies the critical threshold where data becomes unreadable, thereby setting an optimal upper limit that balances processing efficiency and data reliability.
3Measurement precision
If measurements are taken at more number of write times, then accuracy of upper limit setting is improved, but measurement time and complexity increase
Solution Approach 1:
The patent applies partial action by measuring bit error rates at a selective subset of predetermined number of write times rather than measuring at every possible write time. The approximate function can accurately determine the upper limit using measurements from just 3-5 strategically chosen write time points. This partial measurement approach provides sufficient accuracy for setting the upper limit while significantly reducing measurement time and complexity compared to exhaustive measurement of all possible write times.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows for a highly accurate setting of the upper limit of write times, reducing processing time and enhancing data reliability by determining when data becomes unreadable, thus preventing side erase and ensuring data integrity.
Implementation Method 1
a head configured to write data to the disk and read the data from the disk
Implementation Method 2
a so-called 'side erase' may occur due to adjacent track interference (ATI) such as, for example, a leakage of magnetic flux from a head
Data Source
AI summary
A method of setting an upper limit value of the number of write times, which is applied to a magnetic disk device including a disk and a head configured to write data to the disk and read the data from the disk, includes measuring a plurality of bit error rates in a recording area of the disk upon repeatedly writing to an area of the disk adjacent to the recording area a number of write times, deriving a function that approximates a bit error rate in relation to a number of write times, using the measured bit rates corresponding to at least a first number of write times, a second number of write times, and a third number of write times, and applying the function to determine a number of write times that correspond to a first threshold bit error rate that makes the data on the disk unreadable, and setting the determined number of write times as the upper limit value of the number of write times.