SAN Data Tapping Session Modification Mechanism
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Solution Overview
Problem
Current data tapping mechanisms in storage area networks (SANs) lack flexibility and efficiency in managing data flows, particularly in scenarios requiring redirection of READ and WRITE commands, quiescing data I/Os, and handling appliance failures without disrupting host applications.
Innovation Solution
A session modification mechanism that allows appliances to alter data tapping processes by redirecting READ and WRITE commands, quiescing data I/Os, and managing appliance and storage device interactions, including logging WRITE errors and resuming operations, to ensure uninterrupted host application performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If data tapping mechanism intercepts and redirects data flows to appliances, then data accessibility and service capability are improved, but system complexity and difficulty of managing data flows increase
Solution Approach 1:
The patent introduces a session modification mechanism that acts as an intermediary between the data tapping mechanism and the storage area network sessions. This mechanism manages the complexity of intercepting and redirecting data flows by providing a standardized interface for modifying session behavior, handling appliance failures, and controlling data redirection without requiring changes to the core SAN infrastructure.
2Adaptability or versatility
If READ and WRITE commands are redirected to appliance, then data flow control flexibility is improved, but risk of I/O correctness issues and operational disruptions increases
Solution Approach 1:
The session modification mechanism implements dynamic control of data flow redirection, allowing the system to adaptively switch between different operational modes (normal operation, appliance failure, maintenance) based on real-time conditions. This dynamic approach ensures I/O correctness by automatically adjusting redirection behavior to match the current system state, preventing operational disruptions.
Solution Approach 2:
The mechanism incorporates feedback loops that continuously monitor the health and operational status of appliances and storage devices. When appliance failures or maintenance conditions are detected, the system receives feedback and automatically modifies session behavior to maintain I/O correctness, ensuring that data flows are redirected appropriately without causing operational disruptions.
3Reliability
If appliance failures are handled by interrupting data tapping, then system reliability is improved, but host application performance and productivity deteriorate
Solution Approach 1:
The session modification mechanism performs preliminary actions by pre-configuring alternative data paths and redirecting logic before appliance failures occur. When failures are detected, the system can immediately switch to predefined failover modes, maintaining host application performance without interruption. This preliminary preparation ensures both system reliability and continuous productivity during appliance failures or maintenance operations.
Data Source
AI summary
Disclosed is a session modification mechanism for altering a data tapping process in a storage area network (SAN). In general, a data tapping mechanism is set up so that an appliance receives SAN data that is tapped from a particular SAN session. That is, the data tapping mechanism provides to a particular appliance a copy of the SAN data that is being written from a particular host to a particular storage device. The session modification mechanism allows the appliance to alter various aspects of the SAN session that is to be (or is being) tapped. Examples of various modification features includes (i) redirecting READ commands initiated by the host to the appliance and not sending such command to the storage device, (ii) redirecting both READ and WRITE commands initiated by the host to the appliance and not sending such commands to the storage device, (iii) halting redirection and thereby causing READ commands initiated by the host to be sent to the storage device and WRITE commands initiated by the host to be mirrored to both the storage device and appliance, (iv) quiescing and unquiescing all data I/O's for the particular storage device and appliance, and (v) stopping and starting the data tapping mechanism.