Ka'idar CAP ita ce ginshiƙin ka'idar tsarin rarrabawa. Tabbas, jayayyar da ke tattare da ita ba ta raguwa: ma'anar da ke cikinta ba na canonical ba ne, kuma babu wata hujja mai tsauri…
Abin da kawai ba a bayyane yake ba shine ma'anar harafin "P". Lokacin da gungu ya raba, yana yanke shawarar ko ba za a ba da amsa ba har sai an sami adadin ƙididdiga, ko don mayar da bayanan da ke akwai. Dangane da sakamakon wannan zaɓin, ana rarraba tsarin azaman CP ko AP. Cassandra, alal misali, na iya yin ta kowace hanya, ba ya danganta da saitunan tari ba, amma akan ma'auni na kowane takamaiman buƙatu. Amma idan tsarin ba "P" ba ne kuma ya rabu, to menene?
Amsar wannan tambayar ba zato ba ne: gungu na CA ba zai iya rarrabuwa ba.
Wane irin tari ne wannan da ba zai iya tsagawa ba?
Sifa mai mahimmanci na irin wannan tari shine tsarin ajiyar bayanai da aka raba. A mafi yawancin lokuta, wannan yana nufin haɗawa akan SAN, wanda ke iyakance amfani da mafita na CA ga manyan masana'antu waɗanda ke da ikon kiyaye kayan aikin SAN. Domin sabar da yawa suyi aiki tare da bayanai iri ɗaya, ana buƙatar tsarin fayil ɗin tari. Ana samun irin waɗannan tsarin fayil a cikin HPE (CFS), Veritas (VxCFS) da IBM (GPFS).
Farashin RAC
Zaɓin Rukunin Aikace-aikacen Gaskiya ya fara bayyana a cikin 2001 tare da sakin Oracle 9i. A cikin irin wannan gungu, sabar sabar da yawa suna aiki tare da bayanai iri ɗaya.
Oracle na iya aiki tare da tsarin fayil ɗin da aka taru da nasa mafita - ASM, Gudanar da Adana atomatik.
Kowane kwafi yana adana nasa jarida. Ana aiwatar da ma'amala da aikata ta misali ɗaya. Idan misali ya gaza, ɗaya daga cikin nodes ɗin gungu mai tsira (misali) yana karanta log ɗin sa kuma ya dawo da bayanan da suka ɓace - ta haka yana tabbatar da samuwa.
Duk al'amura suna kiyaye ma'ajin nasu, kuma shafuka iri ɗaya (blocks) na iya kasancewa cikin ma'ajin lokuta da yawa a lokaci guda. Bugu da ƙari, idan wani misali yana buƙatar shafi kuma yana cikin ma'ajin wani misali, zai iya samun shi daga maƙwabcinsa ta amfani da tsarin cache fusion maimakon karantawa daga faifai.
Amma menene zai faru idan ɗaya daga cikin al'amuran yana buƙatar canza bayanai?
Bambance-bambancen Oracle shine cewa ba shi da keɓaɓɓen sabis na kullewa: idan uwar garken yana son kulle jere, to ana sanya rikodin kulle kai tsaye akan shafin ƙwaƙwalwar ajiya inda layin kulle yake. Godiya ga wannan tsarin, Oracle shine zakaran wasan kwaikwayo a tsakanin ma'ajin bayanai na monolithic: sabis ɗin kullewa ba zai zama cikas ba. Amma a cikin tsarin tari, irin wannan gine-ginen na iya haifar da matsanancin zirga-zirgar hanyar sadarwa da makullai.
Da zarar an kulle rikodin, misali yana sanar da duk sauran al'amuran cewa shafin da ke adana rikodin yana da keɓaɓɓen riko. Idan wani misali yana buƙatar canza rikodin akan wannan shafi, dole ne ya jira har sai an ƙaddamar da canje-canje ga shafin, wato, an rubuta bayanin canjin zuwa jarida akan faifai (kuma ana iya ci gaba da ciniki). Hakanan yana iya faruwa cewa za a canza shafi a jere ta kwafi da yawa, sannan lokacin rubuta shafin zuwa faifai za ku gano wanda ke adana nau'in wannan shafin na yanzu.
Ƙaddamar da sabunta shafuka guda ɗaya a cikin mabambantan nodes na RAC yana haifar da faɗuwar aikin bayanai da matuƙar girma, har zuwa inda aikin tari zai iya zama ƙasa da na misali guda.
Daidaitaccen amfani da Oracle RAC shine raba bayanai ta zahiri (misali, ta amfani da tsarin tebur da aka raba) da samun dama ga kowane sashe na ɓangarorin ta hanyar keɓewar kumburi. Babban maƙasudin RAC ba shine a kwance ba, amma yana tabbatar da haƙurin kuskure.
Idan kumburi ya daina amsa bugun zuciya, to, kumburin da ya gano shi zai fara aikin jefa kuri'a akan faifan. Idan ba a lura da kullin da ya ɓace ba a nan, to, ɗaya daga cikin nodes yana ɗaukar alhakin dawo da bayanai:
- "daskare" duk shafukan da ke cikin ma'ajiyar kullin da ya ɓace;
- yana karanta rajistan ayyukan (sake sakewa) na kumburin da ya ɓace kuma ya sake yin amfani da canje-canjen da aka rubuta a cikin waɗannan rajistan ayyukan, a lokaci guda yana bincika ko wasu nodes suna da sabbin sigogin shafukan da aka canza;
- mirgina baya jiran ma'amaloli.
Don sauƙaƙe sauyawa tsakanin nodes, Oracle yana da manufar sabis - misali mai kama-da-wane. Misali na iya yin ayyuka da yawa, kuma sabis na iya motsawa tsakanin nodes. Misalin aikace-aikacen da ke aiki da wani ɓangaren bayanan (misali, ƙungiyar abokan ciniki) yana aiki tare da sabis ɗaya, kuma sabis ɗin da ke da alhakin wannan ɓangaren bayanan yana matsawa zuwa wani kumburi lokacin da kumburi ya gaza.
IBM Tsabtace Tsarukan Bayanai don Ma'amaloli
Maganin tari don DBMS ya bayyana a cikin Blue Giant portfolio a cikin 2009. A akida, shine magajin gungu na Parallel Sysplex, wanda aka gina akan kayan aiki na yau da kullun. A cikin 2009, DB2 pureScale an sake shi azaman babban ɗakin software, kuma a cikin 2012, IBM ya ba da na'ura mai suna Pure Data Systems don Ma'amaloli. Bai kamata a ruɗe shi da Tsaftataccen Tsarukan Bayanai don Bincike ba, wanda ba komai bane illa sake suna Netezza.
A kallon farko, tsarin gine-ginen tsarki na Scale yayi kama da Oracle RAC: haka nan, nodes da yawa suna haɗe zuwa tsarin ajiyar bayanai na gama gari, kuma kowane kumburi yana gudanar da nasa misali na DBMS tare da wuraren ƙwaƙwalwar ajiya da rajistan ayyukan kasuwanci. Amma, ba kamar Oracle ba, DB2 yana da keɓaɓɓen sabis na kullewa wanda ke wakilta ta tsarin tsarin db2LLM*. A cikin saitin tari, ana sanya wannan sabis ɗin akan wani kulli na daban, wanda ake kira wurin haɗawa (CF) a cikin Parallel Sysplex, da PowerHA a cikin Tsaftataccen Bayanai.
PowerHA tana ba da ayyuka masu zuwa:
- manajan kulle;
- cache buffer na duniya;
- yankin hanyoyin sadarwa.
Don canja wurin bayanai daga PowerHA zuwa nodes ɗin bayanai da baya, ana amfani da damar žwažwalwar ajiya mai nisa, don haka haɗin haɗin gungu dole ne ya goyi bayan ka'idar RDMA. PureScale na iya amfani da duka Infiniband da RDMA akan Ethernet.
Idan kumburi yana buƙatar shafi, kuma wannan shafi ba ya cikin cache, to, kumburi yana buƙatar shafin a cikin cache na duniya, kuma idan babu shi, karanta shi daga faifai. Ba kamar Oracle ba, buƙatar tana zuwa PowerHA kawai, kuma ba ga nodes na makwabta ba.
Idan misali zai canza jeri, zai kulle shi a keɓantaccen yanayi, da shafin da layin yake cikin yanayin raba. Ana yin rajistar duk makullai a cikin manajan kulle na duniya. Lokacin da cinikin ya ƙare, kumburi yana aika sako zuwa ga manajan makullin, wanda zai kwafi shafin da aka gyara zuwa ma'ajiyar duniya, ya fitar da makullai, kuma ya bata shafin da aka gyara a ma'ajiyar sauran nodes.
Idan shafin da aka gyara layin ya riga ya kulle, to, mai sarrafa makullin zai karanta shafin da aka gyara daga ƙwaƙwalwar kumburin da ya canza, ya saki makullin, ya lalata shafin da aka gyara a cikin cache na sauran nodes, kuma ba da makullin shafin zuwa kumburin da ya buƙace shi.
"Dirty", wato, canza, ana iya rubuta shafuka zuwa faifai duka daga kulli na yau da kullun da kuma daga PowerHA (castout).
Idan ɗaya daga cikin nodes na pureScale ya kasa, farfadowa yana iyakance ga kawai ma'amaloli waɗanda ba a gama su ba a lokacin rashin nasara: shafukan da aka gyara ta wannan kumburi a cikin ma'amaloli da aka kammala suna cikin cache na duniya akan PowerHA. Kullin yana sake farawa a cikin ƙaramin tsari akan ɗaya daga cikin sabobin a cikin tari, yana jujjuya ma'amaloli masu jiran aiki kuma yana sakin makullai.
PowerHA yana aiki akan sabar guda biyu kuma kullin maigidan yana maimaita yanayin sa tare. Idan kumburin PowerHA na farko ya gaza, gungu yana ci gaba da aiki tare da kullin madadin.
Tabbas, idan kun isa ga bayanan da aka saita ta kulli ɗaya, gabaɗayan aikin tarin zai zama mafi girma. PureScale na iya ma lura cewa ana sarrafa wani yanki na bayanai ta kulli ɗaya, sannan duk makullai masu alaƙa da yankin za a sarrafa su a gida ta kumburin ba tare da sadarwa tare da PowerHA ba. Amma da zaran aikace-aikacen ya yi ƙoƙarin samun damar shiga wannan bayanan ta wani kulli, sarrafa makullin tsakiya zai ci gaba.
Gwaje-gwajen cikin gida na IBM akan nauyin aiki na 90% karanta da 10% rubuta, wanda yayi kama da aikin samar da kayan aiki na gaske, yana nuna kusan sikelin layi har zuwa nodes 128. Sharuɗɗan gwaji, abin takaici, ba a bayyana su ba.
HPE NonStop SQL
Fayil ɗin Kamfanin Hewlett-Packard shima yana da nasa dandamalin da ake samu. Wannan shine dandalin NonStop, wanda Tandem Computers ya fitar zuwa kasuwa a cikin 1976. A cikin 1997, Compaq ya sami kamfani, wanda ya haɗu da Hewlett-Packard a 2002.
Ana amfani da NonStop don gina mahimman aikace-aikace - misali, HLR ko sarrafa katin banki. Ana isar da dandalin ne ta hanyar hadaddun software da hardware (na'urar), wanda ya hada da nodes na kwamfuta, tsarin adana bayanai da kayan sadarwa. Cibiyar sadarwa ta ServerNet (a cikin tsarin zamani - Infiniband) tana aiki duka don musanya tsakanin nodes da samun damar shiga tsarin adana bayanai.
Siffofin farko na tsarin sun yi amfani da na'urori masu sarrafawa waɗanda ke aiki tare da juna: duk ayyukan da aka yi tare da na'urori da yawa sun yi aiki tare, kuma da zarar ɗaya daga cikin na'urori ya yi kuskure, an kashe shi, na biyu kuma ya ci gaba da aiki. Daga baya tsarin ya canza zuwa na'urori na al'ada (MIPS na farko, sannan Itanium kuma a ƙarshe x86), kuma an fara amfani da wasu hanyoyin aiki tare:
- saƙonni: kowane tsarin tsarin yana da tagwaye "inuwa", wanda tsarin aiki lokaci-lokaci ke aika saƙonni game da matsayinsa; idan babban tsari ya kasa, tsarin inuwa ya fara aiki daga lokacin da aka ƙayyade ta sakon karshe;
- jefa kuri'a: tsarin ajiya yana da kayan masarufi na musamman wanda ke karɓar dama iri ɗaya kuma yana aiwatar da su kawai idan hanyoyin shiga sun dace; Maimakon aiki tare na jiki, masu sarrafawa suna aiki asynchronously, kuma ana kwatanta sakamakon aikin su kawai a lokacin I/O.
Tun daga 1987, DBMS mai alaƙa tana gudana akan dandamalin NonStop - na farko SQL/MP, daga baya SQL/MX.
Dukkanin bayanan sun kasu kashi-kashi, kuma kowane bangare yana da alhakin aiwatar da tsarin sa na Manajan Samun Bayanai (DAM). Yana ba da tsarin rikodin bayanai, caching, da hanyoyin kullewa. Ana gudanar da sarrafa bayanai ta hanyar Tsare-tsaren Sabar Sabar da ke gudana akan nodes iri ɗaya da masu sarrafa bayanai masu dacewa. Mai tsara tsarin SQL/MX yana rarraba ayyuka tsakanin masu zartarwa kuma yana tara sakamakon. Lokacin da ya zama dole don yin canje-canjen da aka amince da su, ana amfani da ƙa'idar ƙaddamar da ƙa'idodi guda biyu wanda ɗakin karatu na TMF (Ma'amalar Kasuwanci) ya bayar.
NonStop SQL na iya ba da fifikon matakai ta yadda dogayen tambayoyin bincike kar su tsoma baki tare da aiwatar da ciniki. Koyaya, manufarsa ita ce sarrafa gajerun ma'amaloli, ba nazari ba. Mai haɓakawa yana ba da garantin samun gungu na NonStop a matakin "nines" biyar, wato, raguwar lokacin minti 5 ne kawai a kowace shekara.
SAP-HANA
Saki na farko na HANA DBMS (1.0) ya faru a cikin Nuwamba 2010, kuma kunshin SAP ERP ya canza zuwa HANA a watan Mayu 2013. Dandalin yana dogara ne akan fasahar da aka saya: TREX Search Engine (bincike a cikin ajiyar shafi), P * TIME DBMS da MAX DB.
Kalmar “HANA” ita kanta gajarta ce, Babban aikin Analytical Appliance. Ana ba da wannan DBMS a cikin nau'i na lamba wanda zai iya aiki akan kowane sabar x86, duk da haka, ana ba da izinin shigarwar masana'antu akan ingantattun kayan aiki. Ana samun mafita daga HP, Lenovo, Cisco, Dell, Fujitsu, Hitachi, NEC. Wasu saitin Lenovo har ma suna ba da izinin aiki ba tare da SAN ba - aikin tsarin ajiya na gama-gari yana taka ta gungu na GPFS akan fayafai na gida.
Ba kamar dandamalin da aka jera a sama ba, HANA DBMS ce a cikin ƙwaƙwalwar ajiya, watau ainihin hoton bayanan farko ana adana shi a cikin RAM, kuma kawai logs da hotuna na lokaci-lokaci ana rubuta su zuwa diski don murmurewa idan wani bala'i ya faru.
Kowane kullin gungu na HANA yana da alhakin sashin bayanansa, kuma taswirar bayanan ana adana shi a cikin wani yanki na musamman - Server Name, wanda ke kan kullin mai gudanarwa. Ba a kwafin bayanai tsakanin nodes. Hakanan ana adana bayanan kullewa akan kowane kulli, amma tsarin yana da na'urar gano ma'auni na duniya.
Lokacin da abokin ciniki na HANA ya haɗu da cluster, yana zazzage topology ɗin sa sannan zai iya shiga kowane kumburi kai tsaye, gwargwadon bayanan da yake buƙata. Idan ma'amala ta shafi bayanan kumburi guda ɗaya, to ana iya aiwatar da ita a cikin gida ta wannan kumburin, amma idan bayanan nodes da yawa sun canza, kumburin farawa yana tuntuɓar kumburin mai gudanarwa, wanda ke buɗewa da daidaita ma'amalar da aka rarraba, yin ta ta amfani da ingantaccen ƙa'idar ƙaddamar da ƙa'idodi biyu.
An kwafi kullin mai haɗin gwiwa, don haka idan mai gudanarwa ya gaza, kullin madadin yana ɗauka nan da nan. Amma idan kumburin da ke da bayanai ya gaza, to hanya daya tilo ta samun damar bayanansa ita ce ta sake kunna node. A ka'ida, gungu na HANA suna kula da sabar sabar don sake kunna kumburin da ya ɓace da sauri.
source: www.habr.com