Specifications

2
Software Architecture
31
HPI server redundancy
TheRadisy sHPIserverusesaredundancymodelverysimilartotheactive‐standbymodel
usedbytheShelfManager.SincetheHPIserveriscombinedwiththeShelfManagerServer
(ShMS)daemon,itsharesthesameredundancystatuswiththeShelfManager.Theactive
ShelfManagerhoststheactiveHPIserverwhilethestandbyShelfManagerhoststhestandby
HPIserver.Atanypoint oftimeafterHPIserverinitializationiscomplete,thestandbyHPI
serverisfullyredundantwiththeactiveHPIserverandiscapableofassumingtheactiverole
immediatelyfollowingafailover.
TheactiveHPIserverfullycomplieswiththeSAFHPISpecification.Thefullyredundant
standbyHPIservercannotperformcertainactions,suchashot‐swaphandlingandfailovers
duetoplatformandimplementationrestrictionsplacedonthestandbyrole.Althoughitis
possibletoopensessionsonthestandbyHPIserverfornormaloperation,HPIsessionsshould
beopenedonlyontheactiveHPIserverusingthededicated ShelfManagerIPaddressas
DomainId.SeeWritingHPIapplicationsonpage 57forinformationonhowtoopenHPI
sessions.
ThefollowingtypesofHPIdataareactivelysynchronizedwiththepeerHPIservers.
•Sessions–SessionsopenedontheactiveHPIserverpersistoverfailoverstothestandby
ShelfManagerandHPIserver.HPIapplicationscanusethesameSessionIdtoex ecuteHPI
operationsonthesystemfollowingafailover.HPIapplicationsthatopenedthesession
usingthededicatedShelfManagerIPaddressasDomainIdwillnotexperienceany
noticeabledifferenceinHPIserveroperationfollowingafailover,otherthanpossiblya
smalldelayinthenextHPIcommandissuedfollowingthefailover.
•Eventsubscriptions–Sessioneventsubscriptionspersistoverfailovers.Ifanevent
subscriptionwasopenedonasession,itremainsineffectfollowingafailover.Session
eventqueuesarealsosynchronized,ensuringthatnoeventsarelostfromasessionevent
queuethathassubscriptionenabledduetoafailover.
•Domaintag,resourcetag,andresourceseverity–Alluserchangestothedomaintag,
resourcetags,orresourceseveritiesar esynchronizedtothepeerHPI
serverandpersist
followingafailover.
•Eventsandeventlogs–Allevents,bothsystemgeneratedanduseradded,are
synchronizedtothestandbyHPIserver.TheHPIdomainandresourceeventlogsinthe
activeandstandbyHPIserversarethuskeptinsync.Userchangestoeventlogtimesand
eventlogstatesarealsosynchronized.
•Alarms–Allalarms,bothsystemgeneratedanduseradded,aresynchronizedtothepeer
HPIserver.ThedomainalarmtablesintheactiveandstandbyHPIserversarethuskeptin
sync.Userinitiatedchanges,suchasalarmacknowledgementsanduseralarmdeletions,
arealsosynchronized.