Storage Controller Partial Refresh for Low-Power DRAM Retention
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Solution Overview
Problem
Volatile memory devices like DRAM require frequent refresh operations to maintain data reliability, leading to significant power consumption due to the need to refresh both valid and invalid memory regions.
Innovation Solution
A storage controller performs a partial refresh operation by determining a low-power mode based on validity bitmap information, overwriting valid data to inactive memory regions, and storing mapping information, thereby reducing power consumption by only refreshing active sub-blocks with valid data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a full refresh operation is performed on all memory regions, then data reliability is maintained, but power consumption increases significantly
Solution Approach 1:
The memory device is divided into multiple sub-blocks, each capable of independent refresh operations. The controller identifies which sub-blocks contain valid data and applies refresh operations only to those sub-blocks, rather than refreshing the entire memory device. This segmentation enables selective refreshing that maintains data reliability while reducing overall power consumption.
Solution Approach 2:
Different parts of the memory device are treated differently based on their contents. Sub-blocks with valid data receive refresh operations to maintain reliability, while sub-blocks with invalid data are skipped. This local differentiation allows the system to maintain data reliability where needed without unnecessarily consuming power across the entire memory device.
2Reliability
If refresh operations are performed on all sub-blocks, then data reliability is ensured, but power consumption and operational efficiency decrease
Solution Approach 1:
Before performing refresh operations, the controller preliminarily determines which sub-blocks contain valid data by checking validity bitmap information. This preliminary identification allows the controller to prepare and execute refresh operations only on necessary sub-blocks, improving operational efficiency while ensuring data reliability is maintained where data actually exists.
Solution Approach 2:
Instead of performing a complete refresh operation on all sub-blocks, the system applies a partial refresh operation only to sub-blocks that contain valid data. This partial action approach reduces unnecessary operations and improves productivity while still ensuring data reliability is maintained for the actual data storage locations.
Data Source
AI summary
Disclosed is a method of operating a storage controller which includes a volatile memory device. The method includes determining whether a low-power mode is available, based on validity bitmap information indicating invalidity of first data stored in a first memory region of a first sub-block of the volatile memory device and validity of second data stored in a second memory region of a second sub-block of the volatile memory device, overwriting the second data to the first memory region based on the validity bitmap information, in response to determining that the low-power mode is available, storing first mapping information including a fixed index value corresponding to the first memory region and a migration index value corresponding to the overwritten second data in a metadata table, and performing a partial refresh operation corresponding to the first sub-block after overwriting the second data.