Metadata Storage Reservation for Write Throughput in Data Systems

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Solution Overview

Problem

Modern storage systems face challenges when their dedicated metadata storage area reaches capacity, leading to difficulties in accepting new writes, freeing metadata, and increasing available space, as they may enter a state where no additional storage is available, causing system operations to be restricted.

Innovation Solution

Reserving a portion of the metadata storage area for system use and entering a restricted write mode when the non-reserved portion is full, allowing for operations like deleting logical disks and completing cached writes by using the reserved space, thereby freeing space outside the reserved area.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If a dedicated metadata storage area is expanded as needed, then the storage capacity for metadata is improved, but when system usage is high, no additional storage may be available at any given moment, causing the system to refuse new write requests

Engineering Contradiction:

Improvemetadata storage capacityVSAvoidsystem write throughput

Core Design Contradiction:

Quantity of substanceVSProductivity

Solution Approach 1:

The metadata storage area is segmented into a reserved portion and a non-reserved portion. The non-reserved portion is used for normal metadata storage operations, while the reserved portion is preserved as a safety buffer to prevent complete exhaustion of metadata storage space, thereby maintaining system write capability even when the non-reserved portion is full.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The system preliminarily reserves a portion of the metadata storage area before it is needed, proactively preventing the situation where no metadata storage space is available. This advance reservation ensures that critical system operations can always perform metadata updates regardless of current storage utilization levels.

Inventive Principle:

Principle #10Preliminary action

2Quantity of substance

If the dedicated metadata storage area reaches its capacity, then storage efficiency is improved by maximizing space utilization, but the system enters a restricted write state where it cannot accept additional writes

Engineering Contradiction:

Improvemetadata storage utilizationVSAvoidsystem operational continuity

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The system establishes a cushion of reserved metadata storage space in advance, creating a buffer zone that prevents complete exhaustion of storage capacity. This cushioning mechanism ensures that even when the non-reserved portion is fully utilized, the system maintains the ability to perform critical metadata operations, thereby preserving operational reliability.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

3Device complexity

If the free list is stored within metadata, then metadata management is simplified, but when the dedicated metadata storage area is completely full, it may not be possible to free metadata even if an entire logical disk is erased

Engineering Contradiction:

Improvemetadata management complexityVSAvoidmetadata freeing capability

Core Design Contradiction:

Device complexityVSProductivity

Solution Approach 1:

By segmenting the metadata storage area into reserved and non-reserved portions, the system ensures that the free list (stored within metadata) can always write to the reserved portion when needed. This segmentation decouples the metadata freeing capability from the overall storage utilization, allowing metadata to be freed even when the non-reserved portion is completely full.

Inventive Principle:

Principle #1Segmentation

4Stability of the object's composition

If reserved space is protected from encroachment, then system stability is improved, but operations like deleting logical disks and completing cached writes are restricted

Engineering Contradiction:

Improvereserved space integrityVSAvoidsystem operation flexibility

Core Design Contradiction:

Stability of the object's compositionVSAdaptability or versatility

Solution Approach 1:

The system dynamically adjusts the protection level of the reserved space based on operational context. While the reserved space is generally protected from encroachment to maintain stability, the system allows controlled access during critical operations such as deleting logical disks or completing cached writes, thereby balancing stability with operational flexibility.

Inventive Principle:

Principle #15Dynamics

Data Source

PatentUS11237738B2Managing operation of a data storage system with reservation of metadata space

Publication Date: 2022.02.01 EMC IP HLDG CO LLC

AI summary

A method of managing operation of a data storage system (DSS) is provided. The method includes (a) reserving space within a dedicated metadata storage region (DMSR); (b) in response to determining that accommodating a storage request requires use of the reserved space, entering a restricted write mode; (c) while operating in the restricted write mode, using the reserved space in a process that frees space within the DMSR outside the reserved space; and (d) exiting the restricted mode in response to freeing space within the DMSR outside the reserved space. An apparatus, system, and computer program product for performing a similar method are also provided.