Magnetic Disk Controller ATI Block Management
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Solution Overview
Problem
Adjacent track interference (ATI) in magnetic disk devices leads to data readability issues over time, necessitating frequent data rewriting to prevent read difficulties.
Innovation Solution
A magnetic disk device with a controller that estimates ATI influence for each block, sets blocks with high ATI influence and their neighbors as unwritable, and stores write data copies in available, writable blocks until written to the LBA area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If data is continuously written to the same track on a magnetic disk, then write operations can be performed efficiently, but adjacent track interference accumulates and data becomes difficult to read
Solution Approach 1:
The cache area is divided into multiple blocks, and the controller selectively designates specific blocks as unwritable when ATI influence reaches a threshold. This segmentation allows continuous writing to other blocks while protecting vulnerable areas, resolving the contradiction between write efficiency and data readability by spatially distributing write operations across multiple cache blocks.
Solution Approach 2:
The controller proactively identifies blocks where ATI influence reaches the threshold and designates them as unwritable before actual read difficulties occur. This preliminary action prevents ATI accumulation that would lead to read failures, while maintaining write efficiency by redirecting writes to other available blocks rather than waiting for problems to manifest.
2Reliability
If ATI refresh operations are performed to prevent read difficulties, then data readability is maintained, but write performance deteriorates due to frequent rewriting
Solution Approach 1:
The controller proactively designates blocks as unwritable when ATI influence reaches a threshold, preventing ATI accumulation before it causes read failures. This eliminates the need for reactive ATI refresh operations that would deteriorate write performance, as the system prevents the problem rather than correcting it later.
Solution Approach 2:
The invention extracts the problematic blocks from the write pool by designating them as unwritable when ATI influence is high. This separates affected blocks from active write operations, allowing the system to maintain data readability without performing disruptive refresh operations that would harm write performance.
3Productivity
If all blocks in the cache area are used for writing, then cache utilization is maximized, but ATI influence causes data loss during power interruptions
Solution Approach 1:
The controller applies different write policies to different blocks based on their ATI influence levels. Blocks with low ATI influence remain writable and can be fully utilized, while blocks where ATI reaches the threshold are designated as unwritable. This local differentiation maintains high overall cache utilization while protecting data integrity in vulnerable blocks.
Solution Approach 2:
The controller identifies and protects blocks from ATI-induced data loss before power interruptions occur by designating them as unwritable when ATI influence reaches the threshold. This preliminary protection ensures data integrity without significantly reducing cache utilization, as writes are redirected to other available blocks rather than allowing data corruption.
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
Prevents data reading difficulties due to ATI without requiring ATI refresh operations, thereby maintaining write performance and ensuring data integrity during power interruptions.
Implementation Method 1
a magnetic head that writes and reads data to and from the magnetic disk
Data Source
AI summary
According to an embodiment, a magnetic disk is provided with a first area including a plurality of blocks and a second area designated as a write destination by a host. The first memory is a volatile memory that receives write data received from the host. A controller estimates a degree of influence of ATI for each of the plurality of blocks, and sets a first block in which the degree of influence of ATI reaches the first threshold value and two blocks adjacent thereto to be unwritable. The controller selects one of one or more blocks which are not set to be unwritable and have free space among the plurality of blocks, and stores a copy of write data in the first memory in the selected one block at least for a period until the write data is written to the second area.