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Method to operate a Fibre Channel point to point topology in a virtualized environment

IP.com Disclosure Number: IPCOM000238427D
Publication Date: 2014-Aug-26
Document File: 5 page(s) / 48K

Publishing Venue

The IP.com Prior Art Database

Abstract

In a Fibre Channel(FC) point-to-point topology, a sever Host Bus Adapter (HBA) is directly attached to the storage system, which allows the communication between them to use entire bandwidth of the link. The importance of FC point-to-point topology is becoming more prudent with the advent of flash based storage systems. But this topology poses a limitation for the SMB customers on the ability to create multiple Virtual Machine(VM)s on a server. That is, each VM would require a separate physical HBA to be able to access the storage with limitation of the number of I/O ports on the storage server. If the physical HBA is SR-IOV capable and customer wants to leverage the SR-IOV capability of the HBA using VF(Virtual Function) on each VM, today it is not possible with point-to-point configuration. The current article describes how SR-IOV based HBA virtualization can be leveraged when the host HBA is connected to the FC storage in direct attach configuration without a switch.

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Method to operate a Fibre Channel point to point topology in a virtualized environment

Fibre channel(FC) storage is predominantly used in Storage Area Networks (SAN). A switched fabric is a common topology used in the SANs, where both the host Operating system(OS) and the storage subsystems are connected to the switched fabric as shown in Figure-1. This topology enables sharing of the storage with multiple hosts and highly recommended in enterprise environments like data centers. Another type of topology is point-to-point mode, where the FC Host Bus Adapter(HBA) is directly connected to the storage subsystem without a intermediate FC switch as shown in Figure-2. The advantages of point-to-point or direct attach is, it provides full bandwidth connection between the host and storage.

The relevance of direct attach in FC is increasing with the advent of FC flash based storage subsystems. For example flash based storage subsystems can either be in-server (dedicated to the server) or shared storage systems(accessed by multiple hosts in a SAN). In-server storage is meant for dedicated access to the storage. It ensures high speed I/O access, full bandwidth utilization. In-server storage is ideal for applications like stand alone databases or host OS root volume group, dump or paging space devices for OS etc.

Shared storage systems can also function as in-server storage when they are connected in

point-to-point or direct attached mode from the FC HBA on the host. The advantages of the FC direct attach storage configuration are:
1. It eliminates the need for a FC switch, there by reducing the cost. FC switches are very expensive.

2. A SMB customer using only a single server and single storage subsystem who doesn't require a SAN can be benefitted from the direct attach configuration.

Today if a direct attach configuration is used in FC, only one HBA on the host OS will be able to access the storage subsystem. This poses a limitation for the SMB customers on the ability to create multiple Virtual Machine(VM)s on their server. Each VM would require a separate

physical HBA to be able to access the storage with limitation of the number of I/O ports on the storage server. If the physical HBA is SR-IOV** capable and customer wants to leverage the SR-IOV capability of the HBA using VF (Virtual Function) on each VM, today it is not possible with direct attach configuration.

With the current method a SMB customer with single server, single SR-IOV HBA and single storage system who wants to use direct attach configuration, can create several VMs on the server, access the LUNs on the storage server from all the VMs and run I/O from all the VMs. This is a huge advantage for SMB customers who doesn't require a complex SAN.


**SR-IOV is a PCI Special Interest Group (PCI-SIG) standard developed for Virtualization of servers. The SR-IOV specification allows a PCI Express (PCIe) I/O device to appear as multiple

physical and virtual devices which are referred...