REP-1996-218 - A na ly s iso ftheR equestP attern stotheN...

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Unformatted text preview: A na ly s iso ftheR equestP attern stotheN SSDCO n-lineA rch ive TheodoreJohn son C ar losG uerra ted@ c is .u .edu cguerra@ c is .u .edu D ep t .o fC ISE U n ivers ityo fF lor ida G a inesv ille ,FL A b stract Thesuccessfu lim p lem en tat iono fm assstoragearch ivesrequ irecare fu latten t iontoperfor- m anceop t im izat ion s ,toen su rethatthesy stem canhand letheoered load .H ow ever ,perfor- m anceop t im izat ion srequ ireanunderstand ingo fu seraccesspattern s .S inceon-linearch ives andd ig ita llib rar iesaresonew ,litt lein form at ion isava ilab le . TheN at iona lSpaceSc ienceD ataC en ter(N SSDC )o fNA SAG oddardSpaceF ligh tC en ter hasrunanon-linem assstoragearch iveo fspacedata ,theN at iona lD ataA rch iveandD istr i- bu t ionServ ice(NDAD S ) ,s inceN ovem ber .A largew or ld-w idespaceresearchcomm un ity m akesu seo fN SSDC ,request ingm orethan, lesperm on th . S incethein it iat iono fthe ir serv ice ,N SSDChasm a in ta ined logleswh ichrecorda llaccessesthearch ive . Inth isreport ,w ep resen tanana ly s iso ftheNDAD S logles ,spann ingafou ryearper iod (- ) . W eana lyzetheloglesandd iscu sssevera lissues ,inc lud ingcach ing ,re ference pattern s ,changesinu serin terest ,u sercharacter izat ion ,c lu ster ing ,andsy stem load ing . In troduct ion O n-linesc ien t icarch ivesarean increas ing ly im portan ttoo lforperform ingdata-in ten s iveresearch . Bu ild inga large-sca learch iveord ig ita llib rary isanexpen s ivep ropos it ion ,how ever ,andsy stem resou rcesneedtobecare fu llym anaged .T odate ,therehasbeen litt lepub lishedresearchthat stud iestheperform anceo fon-linesc ien t icarch ives . T heN at iona lSpaceSc ienceD ataC en ter(N SSDC )o fNA SAG oddardSpaceF ligh tC en terhas runanon-linem assstoragearch iveo fspacedata ,theN at iona lD ataA rch iveandD istr ibu t ion Serv ice(NDAD S ) ,s inceN ovem ber .A largew or ld-w idespaceresearchcomm un itym akesu se o fNDAD S ,request ingm orethan , lesin (, in ) .S incethein it iat iono f the irserv ice ,theyhavem a in ta ined loglesw h ichrecorda llaccessestotheon-linearch ive . Inth ispaper ,w ep resen tanana ly s iso faccesspattern stotheNDAD S ,basedonthein form a- t ioncon ta ined inthelogles .W ed iscu sssevera laspectso fsy stemperform ance ,inc lud ingthe perform anceo fsevera lcach inga lgor ithm sontherecordedrequeststream ,changesinu serin terest , u sercharacter izat ion ,andtheeect ivenesso fthedatac lu ster ingu sedbyNDAD S .W endthata sm a llcoreo fu sersaccoun tsform ostarch iveact iv ity ,andthatm ostlesarerequested from a few m ed ia .F ina lly ,w ep resen tanana ly s iso fthesy stem load ,nd ingam oderatepos it ivecorre lat ion betw eenda ily load s . T h isresearch issupportedbygran tfromNA SA th roughU SRA ,#-.th roughNA SA#- .P arto f th isw orkw asperform edw h ileT heodoreJohn sonw asanA SEESumm erF acu ltyF e llowatG SFC . P rev iou sW ork Severa lstud iesonthere ferencepattern stom assstoragesy stem shavebeen pub lished .Sm ith ana lyzeslem...
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REP-1996-218 - A na ly s iso ftheR equestP attern stotheN...

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