Heterogeneous NVM Storage with Capacitor-Backed Persistent Memory
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Solution Overview
Problem
Existing battery-backed NVRAM or NVDIMM solutions for enterprise storage have limitations due to small capacity, increased complexity, and the need for batteries, which can be impractical in certain environments, and are limited by the number of devices that can be included, leading to high write latency and cost trade-offs.
Innovation Solution
A storage device with a combination of low-latency persistent memory and higher-latency nonvolatile memory, using a B-tree for indexing write requests and performing garbage collection in nonvolatile memory, while storing write requests in persistent memory, which operates as a circular buffer to manage write requests and optimize latency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If battery-backed NVRAM or NVDIMM is used for write caching, then write latency is reduced, but device complexity increases and batteries are required
Solution Approach 1:
The patent extracts the battery component from the system by using pure capacitor-based power storage. This removes the complexity associated with battery management, replacement, and environmental constraints while maintaining the ability to provide power during transitions. The capacitor-based solution simplifies the overall device architecture by eliminating battery-related subsystems.
Solution Approach 2:
The patent changes the power storage parameter from chemical energy (batteries) to electrical energy storage (capacitors). This parameter change fundamentally alters the system's power management characteristics, enabling faster charge/discharge cycles, improved reliability, and reduced complexity while maintaining energy availability for write caching operations.
2Loss of time
If battery-backed NVRAM or NVDIMM is used for write caching, then write latency is reduced, but the need for batteries makes it impractical in certain environments
Solution Approach 1:
By removing the battery from the system and replacing it with a capacitor-based power storage solution, the patent eliminates the environmental constraints that limit battery usage. Capacitors do not have the same temperature, humidity, or safety restrictions as batteries, making the storage device adaptable to a wider range of environmental conditions including extreme temperatures and hazardous locations.
3Loss of time
If the number of NVRAMs and/or NVDIMMs is increased to reduce write latency, then write latency improves, but cost increases
Solution Approach 1:
The patent merges multiple memory technologies into a unified architecture where capacitor-backed memory works in conjunction with NAND flash memory. This combination allows the system to achieve low write latency through the fast capacitor-based storage while utilizing the high-capacity, lower-cost NAND flash for bulk storage, thereby reducing the need for large quantities of expensive NVRAM/NVDIMM components.
Solution Approach 2:
The heterogeneous storage architecture creates a multi-functional system where different memory types serve different purposes. The capacitor-backed memory handles write caching and journaling operations requiring low latency, while NAND flash provides high-capacity archival storage. This universal design allows a single storage device to fulfill multiple functional requirements, reducing the need for separate specialized components and lowering overall system cost.
Data Source
AI summary
A storage device. The device includes both low-latency persistent memory and higher-latency nonvolatile memory. The persistent memory may be used for write caching or for journaling. A B-tree may be used to maintain an index of write requests temporarily stored in the persistent memory. Garbage collection may be performed in the nonvolatile memory while write requests are being stored in the persistent memory.