Shingled Magnetic Recording Disk Cache Load Reduction
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Solution Overview
Problem
The shingled magnetic recording (SMR) method for disk storage increases recording density but requires a long processing time for rewrite operations due to the need to rewrite data in units of bands, leading to increased load on the media cache and potential delays in response to write commands.
Innovation Solution
A disk storage apparatus with a nonvolatile cache area and a writing controller that writes consecutive data using the SMR method, allowing data to be written directly to user bands instead of the media cache when a spare band is available, thereby reducing the load on the cache and improving rewrite efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If data is written using SMR method with media cache, then recording density is improved, but processing time for rewrite operations increases
Solution Approach 1:
The disk surface is divided into multiple bands, each band containing multiple tracks. The write operation is segmented into band-level operations rather than track-level operations, allowing parallel processing and reducing overall rewrite time while maintaining high recording density through shingled magnetic recording.
Solution Approach 2:
Data is pre-processed and organized into band structures before being written to the disk. The system prepares write commands in advance, grouping consecutive LBAs into band-level operations, which reduces the processing time during actual rewrite operations by avoiding dynamic decision-making during the write process.
2Productivity
If consecutive data is written to media cache until spare band is secured, then rewrite efficiency is improved, but load on media cache increases
Solution Approach 1:
A band management buffer is introduced as an intermediary structure between the media cache and the disk bands. This buffer tracks the status of bands (available, being written, completed) and coordinates write operations, allowing the system to manage cache load more effectively while maintaining high rewrite efficiency through optimized band allocation.
Solution Approach 2:
The system dynamically adjusts the write strategy based on the current state of bands and cache availability. When spare bands are available, data is written directly to bands; when bands are being written, data is directed to media cache. This dynamic adaptation optimizes both rewrite efficiency and cache load management in real-time.
3Quantity of substance
If data is written in units of bands instead of tracks, then recording density is improved, but response time to write commands decreases
Solution Approach 1:
The disk is segmented into bands containing multiple tracks each. By operating at the band level rather than track level, the system achieves higher recording density through shingled magnetic recording while the segmentation allows for optimized write command processing that improves response time through batch operations.
Solution Approach 2:
The system changes the operational parameter from track-level addressing to band-level addressing. This parameter change enables the use of shingled magnetic recording for higher density while the larger operational unit (band) reduces the overhead of command processing, thereby improving response time despite the increased complexity of band management.
Data Source
AI summary
According to one embodiment, a disk storage apparatus includes a storage device, a writing controller, and a controller. The storage device includes a nonvolatile cache area in which a part of consecutive data is temporarily stored. The writing controller is configured to write the consecutive data in a recording area on a disk by an SMR method, the recording area being different from the cache area. The controller is configured to write the part of the data to the cache area, to invalidate data corresponding to logical addresses of the part of the data and recorded in the recording area on the disk, and to set a recording area with the invalidated data recorded therein to be an update recording area in which new data is recordable.