Flash Drive Bootability with Multiple Logical Unit Numbers
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Solution Overview
Problem
Computer systems configured to recognize only a single logical unit number (LUN) or single logical disk are unable to access multiple operating environments on a flash drive, limiting flexibility and security in using portable operating environments.
Innovation Solution
A flash device is configured to initially present itself as a single LUN, with instructions allowing it to reconfigure and expose additional LUNs, enabling the system to boot from multiple logical disks by loading an interpolated LUN driver that reveals hidden LUNs, thus allowing access to multiple operating environments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the flash device presents multiple LUNs initially, then multiple operating environments can be accessed, but the computer system cannot boot properly due to single-LUN configuration requirements
Solution Approach 1:
The flash device performs preliminary actions by presenting only a single LUN during the boot phase, ensuring the computer system can boot reliably. After successful boot, the system then transitions to presenting multiple LUNs to enable access to multiple operating environments, thus resolving the contradiction between bootability and multi-environment access.
Solution Approach 2:
The flash device dynamically changes its LUN presentation behavior based on the operational phase: during boot it presents a single LUN, and after boot it presents multiple LUNs. This dynamic adaptation allows the system to satisfy both the single-LUN boot requirement and the multi-LUN operational requirement.
2Reliability
If the computer system is configured to support only a single LUN, then boot reliability is ensured, but the ability to access multiple operating environments is limited
Solution Approach 1:
The boot process is segmented into distinct phases: the first phase uses a single LUN for reliable booting, and the second phase uses multiple LUNs for accessing different operating environments. This segmentation allows each phase to have optimized characteristics suitable for its specific function.
Solution Approach 2:
The flash device acts as an intermediary that mediates between the computer system's single-LUN boot requirement and the need for multi-environment access. It translates the single-LUN interface during boot into multiple LUNs during operation, enabling both requirements to coexist.
3Adaptability or versatility
If the flash device reconfigures to expose additional LUNs after boot, then multiple operating environments become accessible, but system complexity increases
Solution Approach 1:
The flash device performs self-service by automatically reconfiguring its LUN presentation based on the system state. The device monitors whether the computer system has completed booting and autonomously transitions from single-LUN to multi-LUN mode without requiring manual intervention, thus managing complexity internally while providing simplicity externally.
Data Source
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AI summary
Bootability of a computer system with multiple LUNs. A flash device powers-on into a default LUN, from which the system boots, maintaining any other LUNs unavailable. The first LUN reconfigures the system to remove itself as the available LUN, to load a second LUN as the only available LUN, and to reboot the computer system into the newly available second LUN. The second LUN reconfigures the system to load any additional LUNs, such as removable storage on the flash drive. Upon reconfiguration, the system includes multiple LUNs. The second LUN includes an interpolated LUN driver, which exposes additional LUNs before operation of other device drivers. The interpolated LUN driver takes control during boot-up, exposing any available LUNs before the regular environment's operating system.