Storage Controller Metadata Reconstruction for Power Loss
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Solution Overview
Problem
In storage systems where mapping data is stored in the host's volatile memory, sudden power shutdown can lead to loss of access to data stored in nonvolatile memory devices, as the mapping data becomes unavailable, resulting in unreliable data access.
Innovation Solution
The storage system includes a nonvolatile memory with a controller that generates metadata for user data and writes it continuously with user data and metadata in physical blocks, allowing for reconstruction of mapping data using metadata during a scan operation if the original mapping is lost, ensuring reliable access.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If mapping data is stored in the host's volatile memory for quick access, then access speed is improved, but reliability deteriorates because the mapping data becomes unavailable after sudden power shutdown
Solution Approach 1:
The system performs preliminary actions by continuously storing mapping data in the nonvolatile memory of the storage device during normal operations. This preliminary storage ensures that even if the host's volatile memory loses data due to power shutdown, the mapping data can be retrieved from the nonvolatile memory to reconstruct the mapping table, thereby maintaining reliability without sacrificing access speed.
2Device complexity
If mapping data is stored only in the host, then device complexity is reduced, but reliability deteriorates as the host cannot access data when mapping data is lost
Solution Approach 1:
The system creates a copy of the mapping data in the storage device's nonvolatile memory. This copying mechanism allows the host to maintain a simple architecture while the storage device holds a redundant copy of the mapping data, ensuring that data access reliability is improved without significantly increasing overall system complexity.
3Ease of operation
If the storage device operates in passive mode without storing mapping data, then ease of operation is improved, but reliability deteriorates when the host loses mapping data
Solution Approach 1:
The storage device performs self-service by autonomously storing and maintaining mapping data in its nonvolatile memory. This self-service capability allows the storage device to actively participate in maintaining data accessibility without requiring complex host intervention, thereby improving reliability while maintaining ease of operation.
Data Source
AI summary
A storage device includes a nonvolatile memory including a plurality of physical blocks, a communication interface connectable to a host, and a controller. The controller is configured to generate metadata of host data, which include user data and metadata of the user data, and write, in a physical block of the nonvolatile memory, the metadata of the host data, the metadata of the user data, and the user data continuously in this order, when the host data are received through the communication interface in association with a write command.