Optical Disk RAID Set Using Reject Disks for User Data
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Solution Overview
Problem
Optical disks with surface defects are often discarded as rejects, leading to data storage inefficiencies, as they fail to meet minimum acceptable storage capacity thresholds, and there is a need for a method to utilize these disks effectively while ensuring data integrity.
Innovation Solution
A system and method for constructing parity in an optical disk set that includes a combination of full capacity and less than full capacity disks, where user data is stored on reject disks and parity data is generated and stored on full capacity disks, utilizing RAID techniques to recover data in case of disk failure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If optical disks with surface defects are discarded as rejects, then data storage reliability is maintained, but storage efficiency and resource utilization deteriorate
Solution Approach 1:
The patent changes the usage parameter of reject disks from 'discarded' to 'reused with reduced capacity allocation'. By accepting that reject disks have lower effective capacity due to defects, the system reallocates them for storing user data while maintaining overall system reliability through parity protection mechanisms.
Solution Approach 2:
The patent implements beforehand cushioning by storing parity data on full capacity disks before data loss occurs. This pre-prepared redundancy acts as a cushion that enables recovery of data from reject disks even when they fail, thus maintaining reliability while utilizing otherwise discarded storage resources.
2Productivity
If reject disks are reused for storage, then storage efficiency improves, but data loss risk increases
Solution Approach 1:
The patent introduces parity data as an intermediary element that mediates between the unreliable reject disks and the requirement for data integrity. The parity information stored on full capacity disks serves as a buffer that enables data recovery, thus allowing reject disks to be used without significantly increasing data loss risk.
Solution Approach 2:
The patent changes the reliability parameter through implementing a RAID-like parity protection system. By introducing this additional protection layer, the system can tolerate failures in reject disks while maintaining overall data reliability, thus enabling efficient use of otherwise discarded storage resources.
3Reliability
If parity data is stored on full capacity disks, then data recovery capability improves, but storage capacity for user data decreases
Solution Approach 1:
The patent applies local quality by assigning different roles to different disks based on their capacity and quality characteristics. Full capacity disks are designated for storing parity data due to their superior condition, while reject disks are used for user data. This localized optimization allows the system to achieve both reliability and efficient utilization of available storage resources.
Solution Approach 2:
The patent implements partial action by using only a portion of the full capacity disks' potential storage space for parity data, while the remaining capacity is still available for additional user data or expansion. This partial allocation of full capacity disks to parity storage achieves data recovery capability without completely sacrificing user storage capacity.
Data Source
AI summary
An optical disk RAID set is described that essentially comprises a plurality of optical recording disks including at least one full capacity disk and a plurality of less than full capacity disks. The full capacity disk possessing a rated storage capacity set by an original manufacturer. The less than full capacity disks, which are generally considered reject disks, do not meet the rated storage capacity due to surface flaws or other manufacturing defects. The less than full capacity disks are reserved for user data. Parity is generated from the user data on the less than full capacity disks. The parity data is stored to the full capacity disk.