Virtual Storage Array Booting Over WAN

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Solution Overview

Problem

The latency, bandwidth, and reliability limitations of wide-area networks hinder the consolidation of server computers and associated storage from multiple branch locations into a single location, leading to increased costs and complexity in managing and deploying servers and data storage at branch locations, as well as inefficient use of computing and storage resources.

Innovation Solution

Implementing virtual storage arrays that consolidate data storage at a central data center, using storage block-based protocols like iSCSI, and employing a storage block cache at branch locations to prefetch data based on the behavior of operating systems and applications, thereby hiding WAN limitations and allowing virtualized servers to access data without requiring local storage devices.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If server computers and storage are consolidated at a central location, then equipment costs and administrative complexity are reduced, but WAN latency and bandwidth limitations make data access unacceptably slow

Engineering Contradiction:

Improveadministrative complexityVSAvoiddata access speed

Core Design Contradiction:

Device complexityVSSpeed

Solution Approach 1:

The system performs preliminary actions by prefetching data blocks from the central storage to the branch cache before they are actually needed. The hypervisor monitors I/O patterns and proactively retrieves data that is likely to be accessed soon, thereby reducing the impact of WAN latency when applications need the data.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

A local cache storage device is introduced as an intermediary between the branch location and the central storage. This cache sits at the branch location and holds copies of frequently accessed data blocks, allowing applications to access data locally without suffering from WAN latency, while still enabling centralized storage management.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Speed

If local storage devices are installed at branch locations, then data access performance is improved, but equipment costs and administrative complexity increase

Engineering Contradiction:

Improvedata access speedVSAvoidequipment and administrative costs

Core Design Contradiction:

SpeedVSDevice complexity

Solution Approach 1:

The system merges the benefits of local storage (fast data access) with centralized storage (consolidated management) by implementing a cache at the branch location that is managed through the existing WAN infrastructure. This eliminates the need for separate local storage devices while maintaining performance benefits.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The local cache automatically manages itself by monitoring I/O patterns and prefetching data without requiring manual intervention. The hypervisor and cache work together to autonomously determine what data to cache and when to evict data, reducing administrative overhead while maintaining fast access performance.

Inventive Principle:

Principle #25Self-service

3Adaptability or versatility

If data is accessed frequently over WAN, then centralized storage is utilized, but bandwidth limitations and latency make access unacceptably slow

Engineering Contradiction:

Improvecentralized storage utilizationVSAvoiddata access time

Core Design Contradiction:

Adaptability or versatilityVSLoss of time

Solution Approach 1:

The system performs preliminary data retrieval by prefetching data blocks from central storage to the local cache before applications need them. By analyzing I/O patterns and predicting future access needs, the system proactively transfers data over the WAN during periods when it would otherwise be idle, thereby reducing access time when applications actually need the data.

Inventive Principle:

Principle #10Preliminary action

4Device complexity

If virtualization is used to consolidate servers, then administrative complexity is reduced, but WAN reliability limitations adversely affect mission-critical services

Engineering Contradiction:

Improveadministrative complexityVSAvoidWAN connection reliability

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The local cache acts as a cushion against WAN failures by holding local copies of critical data. When the WAN connection fails or experiences interruptions, applications can continue to access data from the local cache without being affected by the unreliable connection, thereby protecting mission-critical services from WAN reliability issues.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Data Source

PatentUS8677111B2Booting devices using virtual storage arrays over wide-area networks

Publication Date: 2014.03.18 RIVERBED TECH LLC

AI summary

Virtual storage arrays consolidate data storage at a data center for physical and virtual computer systems at one or more branch network locations. Standalone and virtualized computer systems at a branch network location load, execute, and store their operating systems, applications, and data using virtual storage arrays and do not require any built-in or external non-volatile data storage devices such as hard disk drives or solid-state drives at the branch network location. The virtual disks of the virtual storage array are mapped to physical data storage at the data center and accessed via a WAN using storage block-based protocols. A storage block cache at the branch network location includes storage blocks prefetched based on knowledge about the computer systems at the branch network location and the behavior of their operating systems and applications.