{"id":97454,"date":"2020-10-18T14:42:35","date_gmt":"2020-10-18T12:42:35","guid":{"rendered":"https:\/\/prohoster.info\/blog\/administrirovanie\/barery-i-zhurnaliruemye-fajlovye-sistemy"},"modified":"2020-10-18T14:42:35","modified_gmt":"2020-10-18T12:42:35","slug":"barery-i-zhurnaliruemye-fajlovye-sistemy","status":"publish","type":"post","link":"https:\/\/prohoster.info\/et\/blog\/administrirovanie\/barery-i-zhurnaliruemye-fajlovye-sistemy","title":{"rendered":"Barj\u00e4\u00e4rid ja ajakirjandusega seotud failis\u00fcsteemid","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"
\n

Soovime k\u00f5igile head n\u00e4dalavahetust!<\/em><\/strong> Kutsume teid tasuta Demo-tundi <\/em>\u201eVeebiserveri seadistamine (Apache, Nginx, Nginxi koormuse tasakaalustamine)\u201c<\/em><\/a><\/noindex>, mida viib l\u00e4bi Andrei Burano \u2014 UNIX-s\u00fcsteemide spetsialist Mail.Ru Group'is. Samuti avaldame artikli Jonathan Corbet'ilt \u2014 LWN.net'i tegevtoimetaja.<\/em><\/p>\n<\/blockquote>\n

\u017durnaalitavad failis\u00fcsteemid lubavad s\u00fcsteemiadministraatoritel vabaneda kettavigade probleemidest s\u00fcsteemi rikete ajal. Isegi ilma failis\u00fcsteemi terviklikkuse kontrolli k\u00e4ivitamiseta. Kuigi tegelikult on k\u00f5ik veidi keerulisem. Ja nagu n\u00e4itab hiljutine arutelu, v\u00f5ib see olla isegi keerulisem, kui paljud meist arvavad, kuna \u017eurnaalitavate failis\u00fcsteemide terviklikkuse tagamine m\u00f5jutab j\u00f5udlust.<\/p>\n

Failis\u00fcsteem, nagu ext3, kasutab kettal eraldi ala, mida nimetatakse logiks. Failis\u00fcsteemi metainformatsiooni muudatused salvestatakse esmalt logisse ilma \u00fclej\u00e4\u00e4nud failis\u00fcsteemi muutmata. P\u00e4rast k\u00f5igi muudatuste logimiskohta salvestamist lisatakse sinna \u201ekohustuse blokk\u201c, mis n\u00e4itab tehingu l\u00f5petamist. Ja alles p\u00e4rast kohustuse bloki salvestamist fikseeritakse tehing ning muudetud metainformatsioon kirjutatakse kettale. Kui s\u00fcsteem mingil hetkel kokku kukub, saab logis oleva teabe abil t\u00f6\u00f6 l\u00f5petada ja v\u00e4ltida failis\u00fcsteemi kahjustusi, kuna on v\u00e4rskendatud ainult osa metainformatsioonist.<\/p>\n

Kuid on \u00fcks probleem: failis\u00fcsteemi kood peab enne kohustuse bloki kirjutamist olema absoluutselt kindel, et kogu tehingu teave on juba logisse j\u00f5udnud. Lihtsalt \u00f5igesse j\u00e4rjekorda operatsioonide kirjutamine ei ole piisav \u2014 kaasaegsed kettad toetavad suuri sisemisi vahem\u00e4lu ja korraldavad operatsioone \u00fcmber, et j\u00f5udlust parandada. Seet\u00f5ttu tuleb enne kohustuse bloki kirjutamist selgelt n\u00e4idata, et k\u00f5ik logi andmed on kettale \u00fcle kantud. Kui kohustuse blokk kirjutatakse enne, siis v\u00f5ib logi olla kahjustatud. Selle probleemi lahendamiseks kasutatakse barj\u00e4\u00e4re. Sisuliselt keelab barj\u00e4\u00e4r k\u00f5igi blokkide kirjutamise p\u00e4rast barj\u00e4\u00e4ri, kuni k\u00f5ik enne barj\u00e4\u00e4ri kirjutatud blokid on ketta peale kantud. Barj\u00e4\u00e4re kasutades tagavad failis\u00fcsteemid failistruktuuride koosk\u00f5lastatuse.<\/p>\n

Kuid on veel \u00fcks probleem: ext3 ja ext4 failis\u00fcsteemid ei kasuta vaikimisi barj\u00e4\u00e4re. Valik on olemas, kuid kui administraator neid selgelt ei l\u00fclita, toimivad need failis\u00fcsteemid ilma barj\u00e4\u00e4rideta, kuigi m\u00f5nedes jaotustes (n\u00e4iteks SUSE) on vaikeseaded teised. Eric Sandeen otsustas hiljuti, et seda olukorda tuleb muuta ja tegi plaaste<\/u><\/a><\/noindex>, mis muudab vaikeseaded ext3 ja ext4 jaoks. Ja siis algas tormiline arutelu.<\/p>\n

Andrew Morton vastas v\u00e4ga \u00fcksikasjalikult , miks on vaikeseade just selline:<\/u><\/a><\/noindex>Viimati, kui me proovisime seda muuta, halvenes paljude koormuste tulemuslikkus 30%, seet\u00f5ttu viskasin ma k\u00f5ik need plaastrid hirmuga minema. Ma arvan, et me ei saa selle nimel minna ja aeglustada k\u00f5igi masinate t\u00f6\u00f6d nii t\u00f5siselt\u2026<\/p>\n

\n

Siin pole ideaalseid lahendusi ja ma kaldun mitte \u00e4ratama seda magavat koera ning j\u00e4tta vaikeseaded jaotuste arendajate otsustada.<\/em><\/p>\n

Seega on vaikimisi barj\u00e4\u00e4rid v\u00e4lja l\u00fclitatud, kuna need m\u00f5jutavad t\u00f5siselt tulemuslikkust. Lisaks kasutatakse failis\u00fcsteeme \u00fcsna edukalt ka ilma barj\u00e4\u00e4rideta. Teated ext3 failis\u00fcsteemi rikkumisest on haruldased.<\/em><\/p>\n<\/blockquote>\n

Seega on barj\u00e4\u00e4rid vaikimisi v\u00e4lja l\u00fclitatud, kuna need m\u00f5jutavad t\u00f5siselt j\u00f5udlust. Samuti kasutatakse failis\u00fcsteeme \u00fcsna edukalt ilma barj\u00e4\u00e4rideta. Teated ext3 failis\u00fcsteemi kahjustumisest on haruldased ja haruldased.<\/p>\n

Kuid see pole lihtsalt vedamine. Ted Ts'o selgitab<\/u><\/a><\/noindex> see, et ext3 \/ ext4 ajakiri asub tavaliselt katkematult. Esiteks, failis\u00fcsteemi draiver p\u00fc\u00fcab luua selle katkematu. Teiseks, ajakiri luuakse tavaliselt koos failis\u00fcsteemiga, kui katkematu ruumi leidmine on lihtne. Katkematus ja korrastatus on kasulikud mitte ainult j\u00f5udluse jaoks, vaid aitavad ka \u00e4ra hoida \u00fcmberkorraldusi. Tavaliselt asetatakse kommit blok kohe p\u00e4rast teisi andmeid ajakirjas, seega pole kettal p\u00f5hjust \u00fcmberkorraldada. Kommit blok kirjutatakse loomulikult kettale kohe p\u00e4rast ajakirja teisi kirjeid.<\/p>\n

Siiski ei v\u00e4ida keegi, et see nii j\u00e4\u00e4b. K\u00f5vakettad v\u00f5ivad k\u00e4ituda teisiti. Lisaks on logi ringikujuline puhver. Seega, kui tehing logisse kirjutatakse, v\u00f5ib kommitplokk sattuda varasemasse plokki, enne kui muud logikirjed. Nii et kahjustuse t\u00f5en\u00e4osus on alati olemas. Tegelikult on Chris Masonil selle kohta testid<\/u><\/a><\/noindex>. Pole kahtlustki, et barj\u00e4\u00e4ridega t\u00f6\u00f6tamine on v\u00e4hem ohutu kui ilma nendeta.<\/p>\n

Kui olete valmis taluma j\u00f5udluse langust, siis v\u00f5ite barj\u00e4\u00e4ride aktiveerida. Loomulikult juhul, kui teie failis\u00fcsteem ei p\u00f5hine LVM-il (nagu m\u00f5nes jaotuses vaikimisi). Selgub, et seadme kaardistaja ei toeta barj\u00e4\u00e4re. Muudel juhtudel oleks hea v\u00e4hendada j\u00f5udluse kahanemist. Ja tundub, et seda on v\u00f5imalik teha.<\/p>\n

Praegune ext3 rakendus (kui barj\u00e4\u00e4rid on lubatud) teostab iga tehingu korral j\u00e4rgmise toimingute jada:<\/p>\n

    \n
  1. \n

    Andmed kirjutatakse logisse<\/p>\n<\/li>\n

  2. \n

    Teostatakse barj\u00e4\u00e4r<\/p>\n<\/li>\n

  3. \n

    Kirjutatakse kommitplokk<\/p>\n<\/li>\n

  4. \n

    Teostatakse j\u00e4rgmine barj\u00e4\u00e4r<\/p>\n<\/li>\n

  5. \n

    Hiljem m\u00e4rgendatakse metainformatsioon kettale<\/p>\n<\/li>\n<\/ol>\n

    Ext4 puhul saab esimese barj\u00e4\u00e4ri (samm 2) vahele j\u00e4tta, kuna failis\u00fcsteem ext4 toetab logis kontrollsummasid.<\/p>\n

    Kui logi andmed ja kommitplokk on \u00fcmber paigutatud ning toiming katkestatakse rikke t\u00f5ttu, siis logi kontrollsumma ei vasta sellele, mis on salvestatud kommitplokis, ja tehing l\u00fckatakse tagasi. <\/p>\n

    Chris Mason arvab<\/u><\/a><\/noindex>, et oleks \u201e\u00fcldiselt ohutu\u201c eemaldada see barj\u00e4\u00e4r ka ext3-st, v\u00e4lja arvatud juhul, kui logi j\u00f5uab l\u00f5puni ja hakkab uuesti kirjutama algusesse. <\/p>\n

    Veel \u00fcks idee t\u00f6\u00f6 kiirusel paranemiseks on edasil\u00fckata barj\u00e4\u00e4ride toimingud, kui see on v\u00f5imalik. Kui pole otsest vajadust andmed kohe kettale kirjutada, saab logisse luua mitu tehingut ja kirjutada kettale \u00fche barj\u00e4\u00e4riga.<\/p>\n

    Samuti on teatud potentsiaal parandamiseks, korraldades tegevusi hoolikalt, et t\u00f5kked (mis tavaliselt rakendatakse p\u00e4ringute kaudu \u201ek\u00f5ik ootel operatsioonid kirjutada kettale\u201d) ei sunniks kirjeid, mis ei vaja j\u00e4rjestatust.<\/p>\n

    Tundub, et on aeg m\u00f5elda, kuidas teha barj\u00e4\u00e4ride maksumus vastuv\u00f5etavaks. Ted Tso n\u00e4ib arvavat sarnaselt<\/u><\/a><\/noindex>:<\/p>\n

    \n

    Ma arvan, et peaksime lisama barrierid ext3\/4-sse ja seej\u00e4rel t\u00f6\u00f6tama ext4\/jbd2 v\u00e4hendamise p\u00e4rast. T\u00f5en\u00e4oliselt ei t\u00f6\u00f6ta enamik s\u00fcsteeme tingimustes, sarnastes nendele, mida Kris kasutas probleemi demonstreerimiseks, ning failis\u00fcsteemi turvalisus peaks olema prioriteet.<\/em><\/p>\n<\/blockquote>\n

    Mulle \u00fctleb terve m\u00f5istus, et see koer ei maga enam ja ilmselt hakkab ta m\u00f5nda aega haukuma. See v\u00f5ib tekitada muret m\u00f5nede naabrite seas, kuid see on parem kui lasta tal hammustada.<\/p>\n

    Kas on huvitav selles suunas areneda?<\/em><\/strong> Registreeruge tasuta demo-tunniks <\/em>\u201eVeebiserveri seadistamine (Apache, Nginx, Nginxi koormuse tasakaalustamine)\u201c<\/em><\/a><\/noindex> ja osalege \u00fclekanne <\/em>\u201eLogide t\u00f6\u00f6tlemine Linuxis\u201d<\/em><\/a><\/noindex>, mille viib l\u00e4bi Pavel Vikirjuk \u2014 MVNO operaator, DevOps insener. <\/em><\/p>\n

    Allikas: habr.com<\/a> <\/p>","protected":false,"gt_translate_keys":[{"key":"rendered","format":"html"}]},"excerpt":{"rendered":"

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