Gulu la mfundo ziwiri - mdierekezi ali mwatsatanetsatane

Pa Habr! Ndikupereka kwa inu kumasulira kwa nkhaniyi "Node Awiri - Mdyerekezi Ali Mwatsatanetsatane" ndi Andrew Beekhof.

Anthu ambiri amakonda magulu amitundu iwiri chifukwa amawoneka osavuta komanso otsika mtengo 33% kuposa anzawo amitundu itatu. Ngakhale kuti ndizotheka kuyika pamodzi gulu labwino la node ziwiri, nthawi zambiri, chifukwa cha zochitika zosaganiziridwa, kusinthika koteroko kungayambitse mavuto ambiri osadziwika.

Gawo loyamba pakupanga dongosolo lililonse lopezeka kwambiri ndikupeza ndikuyesera kuthetsa zolephera zapayekha, zomwe nthawi zambiri zimafupikitsidwa ngati. SPoF (mfundo imodzi yolephera).

Ndikoyenera kukumbukira kuti n'zosatheka kuthetsa zoopsa zonse za nthawi yopuma mu dongosolo lililonse. Izi zimachokera ku mfundo yakuti chitetezo chodziwikiratu pa chiopsezo ndikuyambitsa kuperewera kwina, zomwe zimabweretsa kuchulukitsitsa kwa dongosolo ndi kutuluka kwa mfundo zatsopano zolephera. Chifukwa chake, poyambira timapanga chiwongola dzanja ndikuyang'ana zochitika zomwe zimagwirizana ndi zolephera zapayekha, osati pamaunyolo okhudzana ndi, chifukwa chake, zochitika zomwe sizingachitike.

Chifukwa cha malonda, sitimangoyang'ana SPoF, komanso kulinganiza zoopsa ndi zotsatira zake, chifukwa chake mapeto a zomwe ziri zovuta ndi zomwe siziri zikhoza kusiyana pa kutumizidwa kulikonse.

Sikuti aliyense amafunikira ena ogulitsa magetsi okhala ndi zingwe zamagetsi zodziyimira pawokha. Ngakhale paranoia idalipira kasitomala m'modzi pomwe kuwunika kwawo kudapeza chosinthira cholakwika. Makasitomala adayimba foni kuyesa kudziwitsa kampani yamagetsi mpaka chosinthira cholakwikacho chidaphulika.

Choyambira chachilengedwe ndicho kukhala ndi mfundo zingapo m'dongosolo. Komabe, dongosololi lisanasunthire mautumiki kumalo omwe atsala atalephera, nthawi zambiri amayenera kuwonetsetsa kuti ntchito zomwe zikuyenda sizikugwira ntchito kwina.

Palibe chotsitsa chamagulu awiri a node ngati kulephera kumabweretsa ma node onse omwe akutumikira tsamba lomwelo. Komabe, zinthu zimasintha ngati zotsatira zake ndikuti onse awiri amayang'anira paokha pamzere wogawana ntchito kapena kupereka mwayi wolembera mosagwirizana ndi nkhokwe yofananizidwa kapena fayilo yogawana.

Choncho, kuti tipewe ziphuphu za deta chifukwa cha kulephera kwa node imodzi - timadalira chinachake chotchedwa "dissociation" (mpanda).

Mfundo ya dissociation

Pamtima pa mfundo ya dissociation ndi funso: kodi mpikisano mfundo kuchititsa chivundi deta? Ngati vuto la data lingakhale vuto, yankho labwino lingakhale kulekanitsa node ku zopempha zomwe zikubwera komanso kusunga kosalekeza. Njira yodziwika kwambiri yodzilekanitsa ndiyo kuchotsa mfundo zolakwika.

Pali magulu awiri a njira zolekanitsa, zomwe ndizitcha mwachindunji и osalunjika, koma angatchulidwe mofanana yogwira и wongokhala. Njira zachindunji zimaphatikizirapo zochita za anzawo omwe atsala, monga kulumikizana ndi IPMI (Intelligent Platform Management Interface) kapena iLO (njira yoyendetsera ma seva pakalibe mwayi wopezeka nawo), pomwe njira zosalunjika zimadalira zomwe zidalephera. kuzindikira mwanjira ina kuti ili pachiwopsezo (kapena kulepheretsa mamembala ena kuti achire) ndikuwonetsa hardware watchdog za kufunika kusagwirizana mfundo analephera.

Quorum imathandizira mukamagwiritsa ntchito njira zachindunji komanso zosalunjika.

Direct dissociation

Pankhani ya kudzipatula kwachindunji, titha kugwiritsa ntchito quorum kuti tipewe mitundu yodzipatula ngati intaneti yalephera.

Ndi lingaliro la quorum, pali zambiri zokwanira m'dongosolo (ngakhale popanda kulumikizana ndi anzawo) kuti node adziwe ngati akuyenera kuyambitsa kupatukana ndi / kapena kuchira.

Popanda quorum, mbali zonse ziwiri za magawo a netiweki aziganiza kuti mbali inayo yafa ndipo adzafuna kulekanitsa inayo. Zikafika poipa, onse awiri amatha kutseka masango onse. Njira ina ndikufanana ndi imfa, kufalikira kosalekeza kwa ma node, osawona anzawo, kuwayambitsanso, ndikuyamba kuchira kuti ayambirenso pomwe anzawo atsatira malingaliro omwewo.

Vuto la kudzipatula ndiloti zipangizo zomwe zimagwiritsidwa ntchito kwambiri zimakhala zosapezeka chifukwa cha zochitika zolephereka zomwe tikufuna kuti tipeze kuchira. Makhadi ambiri a IPMI ndi iLO amaikidwa pa makamu omwe amawalamulira ndipo, mwachisawawa, amagwiritsa ntchito netiweki yomweyi, zomwe zimapangitsa omwe akuwafuna kukhulupirira kuti makamu ena alibe intaneti.

Tsoka ilo, magwiridwe antchito a IPMI ndi zida za iLo sizimaganiziridwanso panthawi yogula zida.

Kupatukana kosalunjika

Quorum ndi yofunikanso pakuwongolera kusagwirizana kwachindunji; ngati atachita bwino, chiwerengero chikhoza kulola opulumuka kuganiza kuti mfundo zotayika zidzasintha kupita kumalo otetezeka pakapita nthawi.

Ndi kasinthidwe uku, chowonera cha hardware chimakhazikitsidwanso masekondi aliwonse a N ngati quorum sitayika. Ngati chowerengera (kawirikawiri machulukitsidwe angapo a N) chitatha, ndiye kuti chipangizocho chimatsitsa mphamvu mopanda chifundo (osati kutseka).

Njirayi ndi yothandiza kwambiri, koma popanda quorum mulibe chidziwitso chokwanira mkati mwa masango kuti muwayendetse. Sikophweka kusiyanitsa pakati pa kuzimitsa kwa intaneti ndi kulephera kwa anzawo. Chifukwa chomwe izi zilili ndikuti popanda kutha kusiyanitsa milandu iwiriyi, mumakakamizika kusankha khalidwe lomwelo pazochitika zonse ziwiri.

Vuto ndi kusankha mode mmodzi ndi kuti palibe njira zimene maximizes kupezeka ndi kupewa imfa deta.

• Ngati musankha kuganiza kuti gulu la anzanu likugwira ntchito koma likulephera, gululo lidzayimitsa mosafunikira mautumiki omwe angakhale akuyenda kuti alipire kutayika kwa mautumiki kuchokera ku node yolephera.
• Ngati mwaganiza kuganiza kuti mfundo yatsika, koma kunali kulephera kwa maukonde ndipo kwenikweni mfundo yakutali ikugwira ntchito, ndiye kuti mukusaina kuti muyanjanitsenso ma data omwe atsatira.

Mosasamala kanthu za zomwe mumagwiritsa ntchito, ndizochepa kupanga kulephera komwe kungapangitse mbali zonse kulephera kapena kuchititsa gulu kutseka ma node omwe atsala. Kusagwiritsa ntchito quorum kumalepheretsa gulu limodzi la zida zamphamvu kwambiri mu zida zake zankhondo.

Ngati palibe njira ina, njira yabwino kwambiri ndiyo kupereka nsembe (pano wolemba akunena za CAP theorem). Kupezeka kwakukulu kwa data yowonongeka sikuthandiza aliyense, komanso kuyanjanitsa ma data osiyanasiyana sikosangalatsa.

Chiwerengero

Quorum ikumveka bwino, sichoncho?

Choyipa chokha ndichakuti kuti mukhale nawo mgulu limodzi ndi mamembala a N, muyenera kukhala ndi kulumikizana pakati pa N/2 + 1 ya node yanu yotsala. Zomwe sizingatheke mumagulu awiri a mfundo pambuyo poti node imodzi yalephera.

Zomwe zimatifikitsa ku vuto lalikulu ndi ma node awiri:
Chiwerengero sichimamveka m'magulu awiri a node, ndipo popanda izo sizingatheke kudziwa modalirika njira yomwe imathandizira kupezeka ndikuletsa kutayika kwa deta.
Ngakhale mu dongosolo la mfundo ziwiri zolumikizidwa ndi chingwe cha crossover, ndizosatheka kusiyanitsa motsimikizika pakati pa kutha kwa netiweki ndi kulephera kwa node ina. Kulepheretsa mapeto amodzi (mwinamwake womwe uli, ndithudi, wofanana ndi mtunda wa pakati pa mfundo) kudzakhala kokwanira kulepheretsa kulingalira kulikonse kuti thanzi la chiyanjano ndilofanana ndi thanzi la bwenzi.

Kupanga magulu awiri a node ntchito

Nthawi zina kasitomala sangathe kapena sakufuna kugula mfundo yachitatu, ndipo timakakamizika kufunafuna njira ina.

Njira 1 - Njira yodzipatula yobwerezabwereza

Chipangizo cha ILO kapena IPMI cha node chikuyimira kulephera chifukwa, ngati sichilephera, opulumuka sangathe kuchigwiritsa ntchito kuti abweretse node pamalo otetezeka. Pagulu la ma node atatu kapena kupitilira apo, titha kuchepetsa izi powerengera quorum ndikugwiritsa ntchito makina owongolera a hardware (njira yodzipatula, monga tafotokozera kale). Pankhani ya ma node awiri, tiyenera kugwiritsa ntchito ma network power distribution unit (PDUs) m'malo mwake.

Pambuyo polephera, wopulumukayo amayesa kulumikizana ndi chipangizo choyambirira chodzipatula (chophatikizidwa ndi iLO kapena IPMI). Ngati izi zapambana, kuchira kumapitilira monga mwanthawi zonse. Pokhapokha ngati chipangizo cha ILO/IPMI chikulephera ndipo PDU imapezeka; ngati mwayiwo ukuyenda bwino, kuchira kungapitirire.

Onetsetsani kuti muyike PDU pa intaneti yosiyana kusiyana ndi magalimoto amagulu, apo ayi kulephera kumodzi kumalepheretsa kupeza zipangizo zonse zodzipatula ndikuletsa kubwezeretsa ntchito.

Apa mutha kufunsa - kodi PDU ndi gawo limodzi lolephera? Kumene yankho liri, ndithudi liri.

Ngati chiwopsezochi chili chofunikira kwa inu, simuli nokha: gwirizanitsani mfundo zonse ku ma PDU awiri ndikuwuza pulogalamu yamagulu kuti igwiritse ntchito poyatsa ndi kuzimitsa. Gululi tsopano likugwirabe ntchito ngati PDU imodzi imwalira, ndipo kulephera kwachiwiri kwa PDU ina kapena chipangizo cha IPMI chidzafunika kuletsa kuchira.

Njira 2 - Kuwonjezera Arbiter

Nthawi zina, ngakhale njira yobwerezera yolekanitsa ndiyotheka mwaukadaulo, ndizovuta pazandale. Makampani ambiri amakonda kukhala ndi kulekana pakati pa oyang'anira ndi eni mapulogalamu, ndipo oyang'anira maukonde osamala zachitetezo sakonda kugawana makonda a PDU ndi aliyense.

Pamenepa, njira yovomerezeka ndiyo kupanga gulu lachitatu lomwe lingathe kuwonjezera chiwerengero cha quorum.

Pakachitika kulephera, node iyenera kuwona ma airwaves a anzawo kapena arbiter kuti abwezeretse ntchito. The arbiter imaphatikizanso ntchito yochotsa ngati ma node onse amatha kuwona arbiter koma sangathe kuwonana.

Njirayi iyenera kugwiritsidwa ntchito molumikizana ndi njira yodzipatula yosadziwika, monga timer watchdog timer, yomwe imapangidwira kupha makina ngati itataya kulumikizana ndi anzawo ndi arbiter node. Chifukwa chake, wopulumuka angaganize momveka bwino kuti mfundo zake zimakhala zotetezeka pambuyo poti nthawi yoyang'anira hardware itatha.

Kusiyana kwakukulu pakati pa arbiter ndi node yachitatu ndikuti arbiter imafuna zinthu zochepa kuti igwire ntchito ndipo imatha kutumikira magulu angapo.

Njira 3 - Chikhalidwe chaumunthu

Njira yomaliza ndi yoti opulumuka apitirizebe kuyendetsa ntchito zilizonse zomwe anali akugwira kale, koma osayambitsa zatsopano mpaka vuto litatha (network kubwezeretsa, node reboot) kapena munthu atenge udindo wotsimikizira kuti mbali inayo yafa.

Bonasi njira

Kodi ndanena kuti mutha kuwonjezera nodi yachitatu?

Zoyika ziwiri

Chifukwa cha kukangana, tiyeni tiyerekeze kuti ndakutsimikizirani za ubwino wa node yachitatu, tsopano tiyenera kuganizira kakonzedwe ka thupi ka mfundozo. Ngati asungidwa (ndi mphamvu) mu rack yomweyo, izi zimapanganso SPoF, ndi zomwe sizingathetsedwe powonjezera rack yachiwiri.

Ngati izi ndizodabwitsa, taganizirani zomwe zingachitike ngati choyikapo chokhala ndi mfundo ziwiri chikalephera, komanso momwe node yotsalira ingasiyanitse pakati pa izi ndi kulephera kwa netiweki.

Yankho lalifupi ndiloti izi sizingatheke, ndipo tikukumananso ndi mavuto onse pa nkhani ya mfundo ziwiri. Kapena wopulumuka:

• amanyalanyaza quorum ndikuyesa molakwika kuyambitsa kukonzanso panthawi yazimitsidwa (kuthekera komaliza kudzipatula ndi nkhani yosiyana ndipo zimatengera ngati PDU ikukhudzidwa komanso ngati amagawana mphamvu ndi ma racks), kapena
• imalemekeza quorum ndikudzilekanitsa nthawi isanakwane pamene mfundo zake zalephera

Mulimonsemo, ma rack awiri sali abwino kuposa amodzi, ndipo ma node amayenera kulandira magetsi odziyimira pawokha kapena kugawidwa patatu (kapena kupitilira apo, kutengera kuchuluka komwe muli nako) ma racks.

Malo awiri a data

Pakadali pano, owerenga omwe salinso pachiwopsezo angafune kulingalira za kubwezeretsa tsoka. Kodi chimachitika ndi chiyani pamene asteroid igunda malo omwewo a data ndi ma node athu atatu akufalikira pazitsulo zitatu zosiyana? Mwachiwonekere Zinthu Zoipa, koma malingana ndi zosowa zanu, kuwonjezera deta yachiwiri sikungakhale kokwanira.

Ngati mwachita bwino, malo achiwiri a data amakupatsirani (ndipo momveka) ndi kopi yamakono komanso yosasinthika ya mautumiki anu ndi deta yawo. Komabe, monga m'magawo awiri, zochitika ziwiri, palibe chidziwitso chokwanira mu dongosolo kuti zitsimikizire kupezeka kwakukulu ndikupewa ziphuphu (kapena kusagwirizana kwa deta). Ngakhale ndi ma node atatu (kapena ma racks), kuwagawira pazigawo ziwiri zokha za data kumasiya dongosololi silingathe kupanga chisankho choyenera pakachitika chochitika (chomwe chili chotheka) chomwe onse awiri sangathe kulumikizana.

Izi sizikutanthauza kuti njira yapawiri ya data center siyenera konse. Makampani nthawi zambiri amafuna kuti munthu adziwe asanatenge njira yodabwitsa yosamukira kumalo osungirako zosunga zobwezeretsera. Ingokumbukirani kuti ngati mukufuna kuyimitsa, mungafunike malo achitatu a data kuti quorum imveke bwino (mwina mwachindunji kapena kudzera pa arbiter), kapena mupeza njira yotsekera zonsezo. pakati.

Source: www.habr.com