NVMe Forward Map Namespace Contiguity
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Solution Overview
Problem
The subdivision of non-volatile memory in SSDs or other devices into multiple namespaces presents challenges for controllers in processing updates to map structures, particularly when new namespaces are added or existing ones are deleted, leading to fragmentation and increased latency.
Innovation Solution
A forward map is maintained with map unit address entries that are grouped into contiguous ranges for each namespace, allowing new namespaces to be added by appending new entries and existing ones to be deleted by shifting down pointers, ensuring the map remains contiguous without fragmentation, and reducing system latencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple namespaces are added to NVM, then storage versatility is improved, but map structure complexity increases
Solution Approach 1:
The forward map is segmented into contiguous ranges, with each namespace occupying a specific contiguous range of map units. This segmentation allows the controller to manage multiple namespaces independently while maintaining a unified forward map structure, reducing the complexity of managing scattered map entries across namespaces.
Solution Approach 2:
The patent introduces a new dimension to namespace management by organizing namespaces along the dimension of contiguous map unit ranges. Instead of managing namespaces as discrete, scattered entities, the system assigns each namespace a contiguous range in the forward map, enabling efficient management through range-based operations rather than individual entry management.
2Adaptability or versatility
If new namespaces are added dynamically, then system adaptability is improved, but processing latency increases
Solution Approach 1:
When a new namespace is added, the controller pre-allocates a contiguous range of map units in the forward map for that namespace. This preliminary action ensures that future operations within the namespace can proceed without needing to search for or allocate additional map units, reducing processing latency for subsequent namespace operations.
Solution Approach 2:
The forward map structure enables namespaces to effectively manage their own map unit allocation. Each namespace maintains its contiguous range, and the controller can quickly determine the range for any namespace through the base MUA array, allowing for self-service style namespace management without complex coordination overhead.
3Productivity
If map units are grouped into contiguous ranges, then data access efficiency is improved, but memory structure complexity increases
Solution Approach 1:
The forward map structure serves multiple functions: it tracks physical locations of map units, organizes data by namespace, and enables efficient range-based queries. By designing the forward map to handle these multiple functions through a unified contiguous range structure, the system achieves data access efficiency without requiring separate complex structures for each function.
Solution Approach 2:
The base MUA array acts as an intermediary between the controller and the forward map. It stores base addresses that point to the start of each namespace's contiguous range in the forward map, simplifying the interface for accessing namespace data while maintaining the benefits of contiguous organization in the forward map itself.
4Adaptability or versatility
If namespaces are managed with separate structures, then namespace independence is improved, but overall system complexity increases
Solution Approach 1:
The patent merges the management of multiple independent namespaces into a single unified forward map structure. By organizing all namespace map units in one contiguous forward map and using base MUA array pointers to delineate namespace boundaries, the system achieves namespace independence through logical separation rather than physical separation, reducing overall management complexity.
Data Source
AI summary
Apparatus and method for managing namespaces in a Non-Volatile Memory Express (NVMe) controller environment. A non-volatile memory (NVM) is arranged to store map units (MUs) as addressable data blocks in one or more namespaces. A forward map has a sequence of map unit address (MUA) entries that correlate each of the MUs with the physical locations in the NVM. The MUA entries are grouped into immediately adjacent, contiguous ranges for each of the namespaces. A base MUA array identifies the address, within the forward map, of the beginning MUA entry for each namespace. A new namespace may be added by appending a new range of the MUA entries to the forward map immediate following the last MUA entry, and by adding a new entry to the base MUA array to identify the address, within the forward map, of the beginning MUA entry for the new namespace.