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Table Of Contents
Getting Started with vSphere Command-Line Interfaces
40 VMware, Inc.
Device Identifiers
Dependingonthetypeofstorage,theESXihostusesdifferentalgorithmsandconventionstogeneratean
identifierforeachstoragedevice.
SCSIINQUIRYidentifiers.ThehostusestheSCSIINQUIRYcommandtoqueryastoragedeviceand
usestheresultingdata,inparticularthePage83information,togenerateauniqueidentifier.SCSI
INQUIRYdeviceidentifiersareuniqueacrossallhosts,persistent,andhaveoneofthefollowingformats:
naa.<number>
t10.<number>
eui.<number>
TheseformatsfollowtheT10committeestandards.SeetheSCSI3documentationontheT10committe
WebsiteforinformationonPage83.
Pathbasedidentifier.IfthedevicedoesnotprovidetheinformationonPage83oftheT10committee
SCSI3documentation,thehostgeneratesanmpx.<path>name,where<path>representsthefirstpathto
thedevice,forexample,mpx.vmhba1:C0:T1:L3.ThisidentifiercanbeusedinthesamewayastheSCSI
inquiryidentifiers.
Thempx.identifieriscreatedforlocaldevicesontheassumptionthattheirpathnamesareunique.
However,thisidentifierisneitheruniquenorpersistentandcouldchangeaftereveryboot.
Typically,thepathtothedevicehasthefollowingformat:
vmhba<adapter>:C<channel>:T<target>:L<LUN>
vmbh<adapter>isthenameofthestorageadapter.Thenamereferstothephysicaladapteronthe
host,nottheSCSIcontrollerusedbythevirtualmachines.
C<channel>isthestoragechannelnumber.SoftwareiSCSIadaptersanddependenthardware
adaptersusethechannelnumbertoshowmultiplepathstothesametarget.
T<target>isthetargetnumber.Targetnumberingisdeterminedbythehostandmightchangeifthe
mappingsoftargetsthatarevisibletothehostchange.Targetsthataresharedbydifferenthosts
mightnothavethesametargetnumber.
L<LUN>istheLUNnumberthatshowsthepositionoftheLUNwithinthetarget.Thenumberis
providedbythestoragesystem.IfatargethasonlyoneLUN,theLUNnumberisalwayszero(0).
Legacy Identifiers
InadditiontotheSCSIINQUIRYormpxidentifiers,ESXigeneratesanalternativelegacyname,calledVML
name,foreachdevice.UsethedeviceUIDinstead.
Examining LUNs
ALUN(LogicalUnitNumber)isanidentifierforadiskvolumeinastoragearraytarget.
Target and Device Representation
IntheESXicontext,thetermtargetidentifiesasinglestorageunitthatahostcanaccess.Thetermsdeviceand
LUNdescribealogicalvolumethatrepresentsstoragespaceonatarget.ThetermsdeviceandLUNmeana
SCSIvolumepresentedtothehostfromastoragetarget.
Different
storagevendorspresenttheirstoragesystemstoESXihostsindifferentways.Somevendorspresent
asingletargetwithmultipleLUNsonit.Othervendors,especiallyiSCSIvendors,presentmultipletargets
withoneLUNeach.