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Method and Apparatus for passing messages between nodes in a cluster over Virtualized Fibre Channel (NPIV) protocol.

IP.com Disclosure Number: IPCOM000236396D
Publication Date: 2014-Apr-24
Document File: 4 page(s) / 37K

Publishing Venue

The IP.com Prior Art Database

Abstract

The nodes in a cluster can also send and receive messages over Fibre Channel link instead of ethernet, when they function as SCSI targets. In a virtualized enterprise environment the cluster nodes can be N_Port ID Virtualization(NPIV) clients. Disclosed is an efficient method, where NPIV clients in a cluster receive the messages without having to implement target mode support. An I/O virtualization server(VIOS) can serve as a target and receive messages on behalf of the NPIV client. VIOS receives the LOGIN requests, SCSI commands etc., on behalf of the NPIV client and finally delivers the message to the NPIV client. The message passing in NPIV environment can take full advantage of this article to allow nodes to communicate with each other through VIOS very efficiently by significantly reducing the overhead of communication over hypervisor and need not to implement target mode on NPIV clients.

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Method and Apparatus for passing messages between nodes in a cluster over Virtualized Fibre Channel (NPIV) protocol.

A cluster environment consists of multiple hosts/nodes managed by cluster management software. The nodes in a cluster communicate typically by passing messages over ethernet.

Nodes can also send/receive messages over Fibre Channel(FC) link instead of ethernet. FC offers a more reliable transport mechanism and enables nodes to communicate even when the ethernet link is down. In a virtualized enterprise environment the cluster nodes can be N_Port ID Virtualization(NPIV) clients and are referred as virtual machines. In such environment, the nodes does not own a physical FC HBA rather a virtual Fibre channel(VFC) port is exported by the I/O Virtualization Server (VIOS) and the VIOS owns the physical HBA. NPIV enables hosts to function
as SAN entities without needing to have a physical HBA. The NPIV clients can run SAN management software and utilities built as per industry standard. When the NPIV clients are acting as nodes in a cluster they may have to communicate by passing messages over NPIV.

The nodes in a cluster should be able to function as SCSI targets to be able to receive the messages over FC. However, hosts typically function as SCSI initiators and Storage devices function as SCSI targets. To enable message passing in a cluster over FC, the hosts should be able to function as SCSI targets as well. The HBA ports that act as SCSI target are said to be functioning in target mode when they are receiving SCSI messages.

To enable message passing in a cluster over FC, it should be sufficient for the FC device driver stack to support a partial target mode functionality. With partial target mode functionality, we support only a well known LUN, LUN 0, which will be reported as a SCSI Processor Type device. Also, this device supports a limited commands like SCSI Send, SCSI inquiry, SCSI test unit ready and task management commands like LUN Reset, Abort Task Set, etc.

In a cluster environment, the nodes send heart beat messages to each other for health checking. The heart beat messages are of fixed and small size and size of messages are pre agreed maximum size. These heart beat messages are sent at regular intervals based on the health check interval of the cluster. The target mode support on a NPIV client enables it to receive the heart beat messages from other nodes. To achieve this each NPIV client need to support target mode and the target mode protocol in NPIV environment involves lot of communication exchange between the NPIV client and VIOS and also whole new driver code to support target mode. This can be significantly reduced to achieve faster inter-node communication in the cluster using the current proposed article.

Lets consider Node A and Node C are part of a cluster. Node A is using NPIV protocol for communicating with SAN and hence called NPIV client. There is a VIOS say B, that enables

NPIV on Node A. Th...