Storage Device UNMAP Data Erasure via Control Unit
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Solution Overview
Problem
Existing storage devices with thin provisioning and deduplication functions face challenges in efficiently erasing data, leading to increased resource loads on host computers and decreased capacity utilization efficiency, while failing to meet legal data erasure requirements.
Innovation Solution
A storage device and method that processes UNMAP commands to cancel the relationship between logical and physical addresses, duplicates data to a new physical page when allocated to multiple logical volumes, and overwrites data with random information to ensure complete erasure, reducing resource loads and maintaining deduplication efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If data is completely erased by overwriting random data on the host computer, then data security requirements are met, but resource load on the host computer becomes huge
Solution Approach 1:
The patent extracts the data erasure function from the host computer and relocates it to the storage device. The storage device receives an UNMAP command from the host computer and independently performs the complete data erasure process by overwriting random data in the specified physical area, thereby meeting data security requirements without imposing heavy resource load on the host computer.
2Reliability
If random data is written to erase data, then complete data erasure is achieved, but data duplication rate decreases leading to reduced capacity utilization efficiency
Solution Approach 1:
The patent applies local quality by differentiating the treatment of data blocks based on their deduplication status. For data blocks that are not duplicated (unique data), random data is written to ensure complete erasure. For data blocks that are duplicated (referenced by multiple logical volumes), the patent uses erasure codes to generate check data that, when combined with remaining data blocks, allows reconstruction of the original data, thereby avoiding random data writing and preserving capacity utilization efficiency.
3Ease of operation
If SCSI UNMAP command is used to release data storage area, then physical area is released, but data remains in the target physical area
Solution Approach 1:
The patent implements preliminary action by performing complete data erasure through random data overwriting (or erasure code-based erasure) before or during the area release process. When the storage device receives an UNMAP command, it first erases the data in the target physical area by writing random data or generating check data using erasure codes, and then releases the physical area for reuse, ensuring both area availability and data security.
Data Source
AI summary
There is provided a storage device that is connected to a computer and receives an UNMAP command to cancel a relationship between a logical address and a physical address provided to the computer, in response to data deletion on the computer. The storage device includes a control unit configured to make data stored in a physical address specified by the UNMAP command irreversible.