Distributed iSCSI Target Host-Level Storage Access
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Solution Overview
Problem
Virtual appliances for iSCSI I/O operations face limitations due to being bound by the scheduler in the hypervisor, leading to potential CPU constraints and impacting turnaround times in processing I/O operations.
Innovation Solution
A virtualization system is configured to support iSCSI targets by distributing storage devices across multiple host machines, allowing iSCSI initiators to access distributed storage devices via the iSCSI protocol, which enables efficient processing and management of I/O operations through a virtualized storage interface and infrastructure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a virtual appliance is used for iSCSI I/O operations, then the system can provide storage services through virtualization, but the virtual appliance is bound by the hypervisor scheduler and may not get enough CPU, impacting turnaround times in processing I/O operations
Solution Approach 1:
The system separates the iSCSI target functionality from the virtual appliance model, allowing the host machine to directly present storage devices as iSCSI targets without going through a virtualized appliance layer. This segmentation eliminates the scheduling overhead while maintaining virtualization benefits for other workloads.
Solution Approach 2:
The patent extracts the iSCSI target processing from the virtualized environment and implements it directly at the host level. By taking out the time-consuming virtualization scheduling layer for this specific function, the system achieves lower I/O latency while preserving virtualization for other purposes.
2Device complexity
If storage devices are centralized in a single location, then management is simplified, but distance limitations of traditional SCSI prevent wide area network access
Solution Approach 1:
The host machine performs multiple functions: it acts as both a virtualization host for running VMs and as a direct iSCSI target for providing storage access. This multi-functionality allows the system to maintain simplified centralized management while enabling wide area network access through the iSCSI protocol over TCP/IP.
Solution Approach 2:
The iSCSI protocol acts as an intermediary that enables SCSI commands to be transmitted over TCP/IP networks. This mediator allows storage devices to be accessed across distance limitations by translating SCSI operations into network-compatible protocols while maintaining the appearance of direct SCSI access.
3Adaptability or versatility
If a virtual appliance executes as a virtual machine, then iSCSI services can be provided in a virtualized distributed storage system, but the virtual appliance must wait its turn in the CPU queue along with all other virtual machines
Solution Approach 1:
The system segments the storage service provision into two paths: general virtualized storage through VMs and time-sensitive iSCSI operations through direct host access. This segmentation allows distributed storage capabilities to be maintained while I/O-critical operations bypass the virtualization overhead.
Solution Approach 2:
The host machine directly provides iSCSI target services without requiring a separate virtual appliance to mediate the operations. By making the host itself serve the iSCSI function, the system eliminates the additional scheduling layer and improves processing throughput while maintaining distributed storage capabilities.
Data Source
AI summary
A given host machine in a virtualization system having a virtual distributed storage system may receive an iSCSI protocol packet from a computer system separate from the given host machine. Processing the iSCSI protocol may include accessing distributed storage device (iSCSI target) comprising storage connected to the two or more host machines in the virtualization system. The given host machine may generate an outbound iSCSI protocol packet comprising return data received from the target and send the outbound iSCSI protocol packet to the computer system.