Memory System Fault Tolerance via Spare DIMM Segmentation
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Solution Overview
Problem
Current memory systems face challenges in detecting and correcting failures, particularly in DIMM modules, which can lead to system crashes due to single RAM device failures, and existing error correction techniques increase costs and complexity while reducing available memory and performance.
Innovation Solution
A memory system with a memory controller and spare memory devices that detects failures and allows for transparent recovery, using a RAID-3 error correction code to correct single symbol errors and maintain system functionality even in the presence of complete DIMM failures, with an innovative application of ECC that enables any memory node to be powered down without data loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing error correction techniques are used, then memory reliability is improved, but cost and complexity increase while available memory and performance decrease
Solution Approach 1:
The memory system is segmented into multiple independent memory modules (DIMMs), each capable of being individually identified and managed. The error correction mechanism is segmented to operate at the module level rather than requiring system-wide complexity, allowing targeted correction of failed modules while preserving the rest of the memory system.
Solution Approach 2:
A memory module identifier mechanism serves as an intermediary between the memory controller and the physical memory modules. This intermediary enables the system to track and manage individual module states, facilitating targeted error correction and recovery without requiring complex system-wide changes.
2Reliability
If a single RAM device fails, then system functionality is maintained with existing ECC, but complete DIMM failures cause system crashes
Solution Approach 1:
The system performs preliminary identification and tracking of memory module states before failures occur. By maintaining awareness of module health and configuration in advance, the system can quickly respond to failures and activate recovery mechanisms without causing system crashes, covering both single device and complete DIMM failure modes.
3Quantity of substance
If memory density increases, then storage capacity is improved, but probability of encountering RAM failure increases
Solution Approach 1:
Large memory systems are divided into multiple smaller, independently managed modules. This segmentation allows the failure of individual modules within high-density systems to be isolated and corrected without affecting the entire memory capacity, maintaining reliability while supporting increased overall storage capacity.
Data Source
AI summary
A system and method for providing a high fault tolerant memory system. The system includes a memory system having a memory controller, a plurality of memory modules and a mechanism. The plurality of memory modules are in communication with the memory controller and with a plurality of memory devices. The plurality of memory devices include at least one spare memory device for providing memory device sparing capability. The mechanism is for detecting that one of the memory modules has failed possibly coincident with a memory device failure on an other of the memory modules. The mechanism allows the memory system to continue to run unimpaired in the presence of the memory module failure and the possible memory device failure.