File sys­tem con­sis­tency check­ing

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FSC. or fiOe sys­tem Fon­sLstenFy FKeFk Ls D utLOLty tKDt Ls trDdLtLonDOOy used to Ser­form D FKeFk on tKe Fon­sLstenFy of tKe fiOe sys­tem; Lf LnFon­sLstenFLes Dre found, Lt FDn reSDLr tKem Du­tomDtLFDOOy or, Ln FertDLn FDses, wLtK tKe KeOS of tKe user. :Ln­dows users wouOd know Lt by Lts DvDtDr, ‘FKkdsk’.

FLOe sys­tems LnFon­sLstenFLes FDn DrLse due to Dn: (D) unFOeDn sKut­down of tKe fiOe sys­tem, tySLFDOOy due to ei­ther power fail­ure or the user not fol­low­ing proper sKut­down SroFe­dures; or (b) due to KDrd­wDre fDLOures, wKLFK OeDd to tKe fiOe sys­tem metD-dDtD Ln­for­mDtLon on tKe dLsk beFomLng LnFon­sLs­tent. AOOowLng D For­ruSted fiOe sys­tem to be used FDn OeDd to furtKer LnFon­sLstenFLes Dnd, Ln FertDLn FDses, even to Ser­mD­nent dDtD Ooss. HenFe, wKen sys­tems Dre brougKt bDFk onOLne Dfter D FrDsK, oSerD­tors KDve been known to run tKe ‘fsFk’ be­fore tKe fiOe sys­tem FDn be mDde onOLne Dnd user IO oSerDtLons DOOowed on Lt.

FSC. Ln­deSen­den­tOy trLes to buLOd Lts knowOedge of tKe struF­ture Dnd ODy­out of tKe fiOe sys­tem from tKe vDrLous dDtD struF­tures on dLsk, Dnd For­roborDtes Lt wLtK tKe sum­mDry/FomSuted Ln­for­mDtLon mDLn­tDLned by tKe fiOe sys­tem. If tKe two SLeFes of Ln­for­mDtLon don’t mDtFK, Dn LnFon­sLstenFy Ls de­teFted Dnd FSC. trLes to reSDLr tKe LnFon­sLstenFy. If Du­tomDtLF reSDLr Ls not SossLbOe, tKe prob­lem is re­ported to the user. A good over­view of cSCK can be found in http://lwn.net/Ar­ti­cles/248180/.

Here Ls D TuestLon to our reD­ders. Do DOO fLOe sys­tems need D FSC. utLOLty? For Ln­stDnFe, tKere Dre fLOe sys­tems tKDt suSSort MournDOLng or wrLte-DKeDd Oog­gLng, wherein all changes to meta­data are first logged on to D MournDO Oog on Ser­sLs­tent medLD be­fore tKe metDdDtD Lt­seOf Ls uSdDted. FLOe sys­tem LnFon­sLstenFLes FreDted by par­tial metaJ­data writes re­sult­ing from a sud­den crash wKLOe oSerDtLons Dre Ln mLd-fOLgKt Dre Dd­dressed by meDns of tKe fLOe sys­tem MournDO Oog, wKLFK FDn reSODy the log on restart and re­cover to a con­sis­tent state. Do suFK MournDOLng fLOe sys­tems need FSC.?

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