SSD Controller Transaction Flag for Lower Page Protection
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Solution Overview
Problem
In solid-state drives (SSDs) with multi-level cell memory, programming upper pages can corrupt previously programmed lower pages, leading to data loss, and existing methods to prevent this are inefficient, requiring unnecessary bandwidth and resource usage.
Innovation Solution
A controller method using a transaction flag to identify and backup at-risk lower pages before programming upper pages, reducing the need for host-managed safe zones and minimizing resource usage by conveying transaction knowledge from the host to the SSD controller.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If host-managed safe zones are used to protect lower pages from corruption during upper page programming, then data integrity is improved, but bandwidth usage and resource consumption increase
Solution Approach 1:
The SSD controller autonomously manages page protection by detecting which lower pages are at risk and backing them up without requiring host intervention. The controller uses transaction flags and word line information to identify vulnerable pages and performs automatic backup operations, eliminating the need for host-managed safe zones and reducing bandwidth consumption.
Solution Approach 2:
The controller performs backup operations before programming upper pages by detecting at-risk lower pages in advance using transaction flags. This preliminary identification and backup of vulnerable pages prevents data loss while minimizing the scope of protection needed, thereby reducing overall bandwidth usage compared to protecting all lower pages.
2Reliability
If all lower pages are backed up before programming upper pages, then data integrity is improved, but processing time and resource usage increase
Solution Approach 1:
The controller applies protection selectively only to lower pages that are actually at risk of corruption, rather than uniformly protecting all lower pages. By using transaction flags and word line information to identify specific vulnerable pages, the system localizes the protection scope, reducing processing time and resource consumption while maintaining data integrity.
Solution Approach 2:
The system changes the parameter of protection scope from all lower pages to only at-risk lower pages by using transaction flags and programming status information. This dynamic adjustment of the protection parameter reduces the number of backup operations required, thereby decreasing processing time while ensuring data integrity for vulnerable pages.
3Loss of energy
If transaction flags are used to identify at-risk pages, then bandwidth usage is reduced, but controller complexity increases
Solution Approach 1:
Transaction flags serve as intermediaries that convey programming transaction information from the host to the controller without requiring direct host intervention for page protection. These flags enable the controller to autonomously determine which lower pages are at risk based on programming status, reducing bandwidth usage while the added complexity is confined to flag processing logic.
Data Source
AI summary
A controller is presented having one or more interfaces through which to communicate with a plurality of memory dies with multi-level memory cells and an interface through which to communicate with a host. The controller also contains a processor that is configured to receive a command from the host to program data in a plurality of lower pages and a plurality of upper pages of the multi-level memory cells. The controller detects an indication from the host that indicates which previously-programmed lower pages from a previous program command are at risk of being corrupted by the programming of the upper pages from the received program command. Prior to programming the upper pages, the controller backs up the previously-programmed lower pages from the previous program command that are at risk of being corrupted but not the lower pages of data programmed by the received program command.