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Table Of Contents
Getting Started with vSphere Command-Line Interfaces
38 VMware, Inc.
Figure 4-1. vSphere Data Center Physical Topology
How Virtual Machines Access Storage
Avirtualdiskhidesthephysicalstoragelayerfromthevirtualmachine’soperatingsystem.Regardlessofthe
typeofstoragedevicethatyourhostuses,thevirtualdiskalwaysappearstothevirtualmachineasamounted
SCSIdevice.Asaresult,youcanrunoperatingsystemsthatarenotcertified
forspecificstorageequipment,
suchasSAN,inthevirtualmachine.
Whenavirtualmachinecommunicateswithitsvirtualdiskstoredonadatastore,itissuesSCSIcommands.
Becausedatastorescanexistonvarioustypesofphysicalstorage,thesecommandsareencapsulatedintoother
forms,dependingontheprotocolthatthe
ESXihostusestoconnecttoastoragedevice.
Figure 42depictsfivevirtualmachinesthatusedifferenttypesofstoragetoillustratethedifferencesbetween
eachtype.
Figure 4-2. Virtual Machines Accessing Different Types of Storage
server
group 1
virtual machines
server
group 2
server
group 3
fibre channel
storage array
iSCSI
storage array
NAS
storage array
vCenter Server
terminal
Web access
vSphere Client
fibre channel switch fabric / IP network
ESX/ESXi
VM VM VM
VM VM VM
iSCSI array NAS appliancefibre array
Host
VMFS
local
ethernet
SCSI
VMFS VMFS NFS
virtual
machine
virtual
machine
virtual
machine
virtual
machine
virtual
machine
SAN LAN LAN LAN
iSCSI
hardware
initiator
fibre
channel
HBA
ethernet
NIC
ethernet
NIC
software
initiator
requires TCP/IP connectivity
Key
physical
disk
datastore
virtual
disk