Multi-Actuator Read-After-Write for Hard Disk Drives
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Solution Overview
Problem
Conventional hard disk drives (HDDs) face performance delays due to the need to wait for at least one disk revolution to verify successful write operations, which reduces overall performance, especially with increasing areal density and the implementation of heat-assisted magnetic recording (HAMR).
Innovation Solution
Implementing a read-after-write methodology using multiple independent actuators and read/write heads that allow data verification within less than one disk revolution by simultaneously writing and reading data using multiple heads accessing the same disk surface, with a controller verifying the written data using a second read head after the write operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If a single actuator performs both write and read operations sequentially, then device complexity is reduced, but verification time increases to at least one full disk revolution
Solution Approach 1:
The system divides the actuator resources into separate write and read functions by using multiple actuators, where at least one actuator is dedicated to writing and another to reading. This segmentation allows concurrent write and read operations on the same disk surface, reducing verification time from one full revolution to less than one revolution.
Solution Approach 2:
The patent transitions from sequential single-actuator operation to parallel multi-actuator operation by adding spatial dimensionality to the actuator configuration. Multiple actuators operate simultaneously on the same disk surface, enabling the read operation to occur during the same disk revolution that the write operation occurs, rather than waiting for the next revolution.
2Productivity
If multiple actuators operate independently on the same disk surface, then data rate and throughput increase, but device complexity increases
Solution Approach 1:
The system merges the operations of multiple actuators under a unified controller that coordinates write and read operations on the same disk surface. This merging allows the benefits of parallel operation (increased throughput and data rate) while managing complexity through centralized control logic that schedules and synchronizes actuator movements.
Solution Approach 2:
The controller is designed with universal functionality to manage multiple actuators, handling both write and read operations, and coordinating their independent movements. This multi-functional controller reduces the need for separate specialized control systems for each actuator, thereby managing complexity while enabling high throughput.
3Speed
If verification is performed within less than one revolution, then performance improves, but precision requirements for actuator positioning increase
Solution Approach 1:
The system performs preliminary positioning of the read actuator to the target track before the write actuator completes its write operation. This preliminary action allows the read head to be in position and ready to verify data immediately after writing, enabling verification within less than one revolution while maintaining positioning accuracy through advance preparation.
Solution Approach 2:
The controller uses feedback mechanisms to monitor and adjust actuator positions in real-time, ensuring precise positioning for both write and read operations. This feedback control compensates for the tighter timing constraints imposed by sub-revolution verification, maintaining positioning precision despite the increased speed requirements.
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 significantly enhances HDD performance by reducing verification time, increasing data rate, and allowing for improved throughput and capacity utilization by enabling concurrent read and write operations across the same disk surface.
Implementation Method 1
write data to a track on the first recording surface using the first write head
Implementation Method 2
perform a read operation on the data written to the track using the second read head
Implementation Method 3
one or more magnetic recording disks coupled to a spindle motor
Data Source
AI summary
One or more magnetic recording disks are coupled to a spindle motor, each of the disks having opposing recording surfaces. Two or more actuators are moveable independently over at least a first recording surface of the one or more disks. A first actuator of the two or more actuators comprises a first write head and a first read head. A second actuator of the two or more actuators comprises at least a second read head and may include a second write head. A controller is coupled to the two or more actuators and configured to write data to a track on the first recording surface using the first write head, and perform a read operation on the data written to the track using the second read head. The controller is also configured to verify that the data was successfully written to the track in response to the read operation. The read operation can be performed within less than one revolution of the first recording surface after the write operation.