Rank Sparing for Memory Redundancy and Capacity
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Solution Overview
Problem
Traditional DIMM sparing techniques in modern computer systems require significant memory overhead and reduced configuration flexibility, leading to decreased memory capacity and performance, especially at higher operating frequencies.
Innovation Solution
Implementing rank sparing, where one rank per channel is reserved as a spare, allowing for more flexible DIMM loading and configuration, with all ranks on a channel being of the same type, reducing memory overhead and increasing usable capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If DIMM sparing is implemented to provide memory redundancy, then system reliability is improved, but memory overhead increases and usable capacity decreases
Solution Approach 1:
The invention segments the DIMM structure into multiple ranks, allowing sparing to be implemented at the rank level rather than the entire DIMM level. This segmentation enables finer-grained redundancy management where only the failed rank needs to be migrated to a spare rank on a different DIMM, rather than migrating all data from a failed DIMM. The patent specifically divides DIMMs into ranks and implements sparing by migrating individual ranks between DIMMs, thereby reducing the overhead associated with traditional DIMM-level sparing.
2Reliability
If DIMM sparing is implemented to ensure memory reliability, then system reliability is improved, but configuration flexibility is reduced
Solution Approach 1:
By segmenting the sparing mechanism to operate at the rank level rather than DIMM level, the system gains flexibility in DIMM configurations. Different DIMM capacities and types can be mixed more freely since the sparing operation only requires matching rank structures, not entire DIMM specifications. This enables more adaptable memory system configurations while maintaining reliability through rank-level redundancy.
3Reliability
If traditional DIMM sparing is used to provide memory redundancy, then system reliability is improved, but memory performance decreases due to overhead
Solution Approach 1:
The rank-level segmentation reduces the volume of data that needs to be managed for sparing operations. Instead of treating entire DIMMs as atomic units for redundancy, the system operates on individual ranks, which are smaller subsets of memory. This reduction in operational scope decreases the overhead associated with sparing management and improves overall memory performance while maintaining the same level of reliability.
Data Source
AI summary
A system, and a corresponding method, are used to implement rank sparing. The system includes a memory controller and one or more DIMM channels coupled to the memory controller, where each DIMM channel includes one or more DIMMS, and where each of the one or more DIMMs includes at least one rank of DRAM devices. The memory controller is loaded with programming to test the DIMMs to designate at least one specific rank of DRAM devices as a spare rank.