Daisy-Chained Sideband Routing for Independent Hard Drive Control
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Solution Overview
Problem
Conventional storage enclosures lack the ability to control individual hard drives independently, requiring all drives to be shut down for maintenance or power management, and are limited by crosstalk issues due to the large number of PCB traces needed for data and command transmission.
Innovation Solution
A storage enclosure design with daisy-chained sideband signal routing and distributed complex logic devices (CPLDs) allows for fine-grained control of hard drives, enabling individual power management and operation state changes without affecting other drives, using separate sideband cables for management commands instead of PCB traces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a single large PCB with embedded traces is used to connect all hard drives to the expander, then data transmission between hard drives and expander is enabled, but crosstalk increases and the number of hard drives must be limited
Solution Approach 1:
The invention divides the storage enclosure into multiple independent zones, each with its own PCB and expander. Hard drives are distributed across these zones rather than all connected to a single large PCB. This segmentation reduces the number of traces on each individual PCB, thereby reducing crosstalk while still allowing a large total number of hard drives in the enclosure.
2Ease of operation
If power management commands are transmitted via the same PCB traces as data, then command transmission is simplified, but individual drive control is lost and all drives must be shut down simultaneously
Solution Approach 1:
The invention separates power management command transmission from data transmission by providing dedicated command paths through individual expanders. Each expander can receive and process power management commands independently for its associated hard drives, enabling individual drive control without affecting other drives. This segmentation of control functions increases device complexity slightly but enables fine-grained individual drive management.
3Device complexity
If a single large PCB is used to accommodate all hard drives, then the storage enclosure structure is simplified, but the PCB traces must be numerous which induces crosstalk
Solution Approach 1:
Instead of one large PCB, the invention uses multiple smaller PCBs distributed throughout the enclosure, each serving a subset of hard drives. Each PCB has fewer traces, reducing crosstalk. The overall structure is managed by multiple expanders that coordinate to maintain system simplicity while avoiding the crosstalk problems of a single large PCB.
4Quantity of substance
If the number of PCB traces is increased to support more hard drives, then more hard drives can be connected, but crosstalk between traces increases
Solution Approach 1:
The invention distributes hard drives across multiple PCBs and expanders rather than connecting all drives to a single PCB. This segmentation ensures that each PCB has a manageable number of traces, avoiding crosstalk issues while still supporting a large total number of hard drives through the combined capacity of multiple PCBs.
Data Source
AI summary
A storage enclosure includes a plurality of hard drive sub-boards, each configured to include a plurality of hard drives. A local logic device manages each hard drive sub-board. A master logic device manages the local logic devices. The master logic device receives management commands from a host computer system coupled to the storage enclosure, and routes those commands to specific local logic devices. The local logic devices then relay the commands to specifically targeted hard drives. Thus, each hard drive within the storage enclosure can be independently controlled, allowing a single hard drive to be powered down without powering down other hard drives in the enclosure.