Filemark Cache for Virtual Tape Libraries

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Solution Overview

Problem

Virtual tape libraries face inefficiencies in moving between filemarks due to the need for random, small reads across large numbers of filemarks, which can overwhelm storage appliances and are not optimized for sequential I/O, especially when deduplication and other file system processing are involved.

Innovation Solution

Implementing a filemark cache with a splay tree organization structure that allows for efficient access and movement between filemarks by caching metadata, reducing the need for frequent reads from the virtual tape file and improving sequential and non-sequential access.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If virtual tape libraries use traditional file system methods to access filemarks, then data can be stored and retrieved, but the random, small reads required to move between filemarks overwhelm storage appliances and degrade performance

Engineering Contradiction:

Improvespeed of moving between filemarksVSAvoidload on storage appliance

Core Design Contradiction:

ProductivityVSObject-generated harmful factors

Solution Approach 1:

The patent pre-calculates and stores metadata about filemark positions, distances, and paths before they are needed. When a move command is received, the system uses this pre-computed metadata to directly navigate between filemarks without performing random reads during the actual move operation, thus eliminating the performance bottleneck.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent introduces a virtual tape library layer with a command parser and metadata structure that acts as an intermediary between the file system and the storage appliance. This intermediary translates high-level move commands into efficient operations using pre-computed metadata, preventing the generation of harmful random read patterns on the storage appliance.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Adaptability or versatility

If virtual tape libraries emulate physical tape libraries to maintain compatibility with backup applications, then existing software can be used without modification, but the file system is not optimized for sequential I/O operations

Engineering Contradiction:

Improvecompatibility with backup applicationsVSAvoidefficiency of I/O operations

Core Design Contradiction:

Adaptability or versatilityVSProductivity

Solution Approach 1:

The patent creates a virtual copy of the physical tape library interface that emulates tape commands and operations. This virtual layer copies the behavior of physical tapes while using an optimized metadata-driven approach underneath, allowing compatibility with backup applications while achieving superior I/O efficiency through sequential access patterns enabled by pre-computed filemark information.

Inventive Principle:

Principle #26Copying

Data Source

PatentUS9152352B1Filemark cache to cache filemark metadata for virtual tapes

Publication Date: 2015.10.06 EMC IP HLDG CO LLC

AI summary

A method of an aspect includes receiving a request to move between filemarks at a network interface. A filemark cache is accessed with an offset into an open virtual tape file based on the received request. A determination is made that the offset is in the filemark cache. Filemark metadata corresponding to the offset is read from the filemark cache. The filemark cache is separate from the open virtual tape file. Other methods, apparatus, and articles are also disclosed.