vsphere-esxi-vcenter-server-55-storage-guide

Using ESXi with Fibre Channel SAN 3When you set up ESXi hosts to use FC SAN storage arrays, special considerations are necessary. This sectionprovides introductory information about how to use ESXi with a FC SAN array.This chapter includes the following topics:• “Fibre Channel SAN Concepts,” on page 35• “Using Zoning with Fibre Channel SANs,” on page 36• “How Virtual Machines Access Data on a Fibre Channel SAN,” on page 37Fibre Channel SAN ConceptsIf you are an ESXi administrator planning to set up hosts to work with SANs, you must have a workingknowledge of SAN concepts. You can find information about SANs in print and on the Internet. Becausethis industry changes constantly, check these resources frequently.If you are new to SAN technology, familiarize yourself with the basic terminology.A storage area network (SAN) is a specialized high-speed network that connects computer systems, or hostservers, to high performance storage subsystems. The SAN components include host bus adapters (HBAs)in the host servers, switches that help route storage traffic, cables, storage processors (SPs), and storage diskarrays.A SAN topology with at least one switch present on the network forms a SAN fabric.To transfer traffic from host servers to shared storage, the SAN uses the Fibre Channel (FC) protocol thatpackages SCSI commands into Fibre Channel frames.To restrict server access to storage arrays not allocated to that server, the SAN uses zoning. Typically, zonesare created for each group of servers that access a shared group of storage devices and LUNs. Zones definewhich HBAs can connect to which SPs. Devices outside a zone are not visible to the devices inside the zone.Zoning is similar to LUN masking, which is commonly used for permission management. LUN masking is aprocess that makes a LUN available to some hosts and unavailable to other hosts.When transferring data between the host server and storage, the SAN uses a technique known asmultipathing. Multipathing allows you to have more than one physical path from the ESXi host to a LUN ona storage system.Generally, a single path from a host to a LUN consists of an HBA, switch ports, connecting cables, and thestorage controller port. If any component of the path fails, the host selects another available path for I/O. Theprocess of detecting a failed path and switching to another is called path failover.VMware, Inc. 35