Storage Network Switch Stack Isolation via SAS Expanders
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Solution Overview
Problem
The exponential increase in data access latency with the depth of storage shelves in a storage system limits the storage size, as deeper shelves lead to larger latency, restricting the number of shelves and mass storage devices that can be effectively utilized.
Innovation Solution
Implementing a storage network switch that interconnects multiple storage stacks to form a single Serial Attached SCSI (SAS) domain, isolating stacks from each other to prevent communication and using expanders with smaller routing tables, reducing the need for costly high-speed memory and enabling dynamic connection of storage host devices and stacks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If storage shelves are connected in a linear chain fashion to increase storage capacity, then the number of mass storage devices increases, but data access latency increases exponentially
Solution Approach 1:
The patent divides the storage system into multiple independent storage stacks, each with its own expander device. This segmentation allows each stack to operate independently with its own routing table, preventing latency propagation across the entire system when one stack is accessed. The storage system is segmented into manageable units that can be accessed in parallel.
Solution Approach 2:
The patent introduces expander devices as intermediaries between storage shelves and the SAS switch. These expanders act as mediators that manage routing decisions locally within each storage stack, reducing the need for messages to traverse the entire linear chain. The expander devices mediate communication between storage devices and the switch, enabling more efficient data access.
2Quantity of substance
If the number of storage shelves is increased to expand storage capacity, then the storage size increases, but the routing table size required by expanders increases
Solution Approach 1:
The patent segments the routing function by assigning each expander device responsibility for only its local storage stack's routing information. Instead of requiring a single expander to maintain routing tables for all storage devices in the system, each expander maintains a localized routing table for its own stack, significantly reducing the routing table size requirement.
Solution Approach 2:
The patent implements local quality by making each expander device's routing table specific to its local storage stack rather than requiring a global routing table. Each expander maintains routing information only for devices within its own stack, creating locally optimized routing tables that are much smaller in size.
3Speed
If high-speed memory is used in expanders to store routing tables, then routing performance improves, but system cost increases
Solution Approach 1:
The patent segments the routing table storage requirement across multiple smaller expander devices rather than requiring one large expander with a large routing table. Each expander needs only a small portion of routing table memory, which can be implemented with less expensive memory components, reducing overall system cost while maintaining performance.
Solution Approach 2:
The patent enables the use of less expensive memory in expander devices by reducing the memory requirements through localized routing tables. Instead of requiring expensive high-capacity high-speed memory in each expander, the system can use more economical memory solutions that are sufficient for the reduced routing table size.
Data Source
AI summary
Technology is disclosed for stack isolation in a storage system including a storage network switch and multiple storage sub-systems (e.g., storage stacks). The storage network switch includes multiple ports and at least one of the ports is configured to dynamically connect to a device that can be either a storage controller device or a storage sub-system. The technology can receive an identification message indicating that a device is connected to a port of a storage network switch, determine based on the identification message at the storage network switch whether the device is a storage controller device or a storage sub-system, and transfer messages between the ports of the storage network switch such that the storage network switch prevents communications between storage sub-systems connected to the storage network switch, but allows communications between the storage sub-systems and storage controller devices connected to the storage network switch.