iSCSI Initiator Demand-Paging Priority via 802.1q Tagging
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Demand-paging iSCSI traffic in Ethernet networks faces suboptimal performance due to competing with lower-priority network traffic, leading to increased network latencies.
Innovation Solution
Assigning Ethernet user priority to demand-paging iSCSI requests by using a flag in SCSI command descriptor blocks, mapping it to IEEE 802.1q user priorities, and transmitting these requests over the Ethernet network to prioritize demand-paging operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If demand-paging iSCSI traffic is transmitted over Ethernet network without priority marking, then network infrastructure complexity is reduced, but network latency increases due to competition with lower-priority traffic
Solution Approach 1:
The patent changes the parameter of Ethernet frame priority by mapping SCSI command descriptor block flags to IEEE 802.1q user priority values. This allows demand-paging traffic to be differentiated and prioritized without changing the fundamental Ethernet infrastructure, resolving the contradiction between maintaining simple infrastructure and reducing latency through priority marking.
2Loss of time
If demand-paging iSCSI traffic is prioritized using Ethernet user priority, then network latency is reduced, but system complexity increases due to priority mapping and flag processing
Solution Approach 1:
The system uses existing OS-level paging flags (such as the paging I/O flag in Windows) to automatically identify demand-paging traffic. The iSCSI initiator then maps these existing flags to Ethernet priority levels without requiring external intervention or complex external control systems, allowing the system to self-differentiate and prioritize traffic based on already-available information.
Solution Approach 2:
The patent makes the iSCSI protocol multi-functional by enabling it to carry both data transfer and priority indication functions within the same command descriptor block structure. The existing CDB flags serve dual purposes: identifying command types and indicating priority levels, thereby reducing the need for separate priority marking mechanisms and minimizing additional system complexity.
3Ease of operation
If all iSCSI traffic is treated equally without priority differentiation, then protocol simplicity is maintained, but demand-paging performance deteriorates due to latency from competing traffic
Solution Approach 1:
The patent applies local quality differentiation by assigning specific priority levels to specific types of iSCSI traffic based on their CDB flags. Rather than changing the entire protocol's treatment of all traffic, it locally differentiates demand-paging traffic from other iSCSI traffic by mapping the paging flag to higher Ethernet priority values, thereby improving demand-paging performance while maintaining protocol simplicity for other traffic types.
Data Source
AI summary
One embodiment of the present invention sets forth a technique for establishing high user priority for Ethernet frames related to demand-paging operations over iSCSI. The iSCSI initiator is configured to identify demand-page operations using techniques specific to the operating system and to set the 802.1q tag control information (TCI) user priority bit field to reflect high priority for demand-page related Ethernet frames. The demand-page related Ethernet frames are then delivered to the iSCSI target with a higher priority through the intervening Ethernet network than other traffic. Overall performance of demand paging operations is improved relative to prior art systems through an average reduction in network latency.