▁In ▁all ▁three ▁modes , ▁the ▁internal ▁structure ▁of ▁file ▁system ▁is ▁assured ▁to ▁be ▁consistent ▁even ▁after ▁a ▁crash . ▁In ▁any ▁case , ▁only ▁the ▁data ▁content ▁of ▁files ▁or ▁directories ▁which ▁were ▁being ▁modified ▁when ▁the ▁system ▁crash ed ▁will ▁be ▁affected ; ▁the ▁rest ▁will ▁be ▁int act ▁after ▁recovery . ▁ ▁Dis adv antages ▁ ▁Function ality ▁Because ▁ext 3 ▁a ims ▁to ▁be ▁back ward - compatible ▁with ▁the ▁earlier ▁ext 2 , ▁many ▁of ▁the ▁on - disk ▁structures ▁are ▁similar ▁to ▁those ▁of ▁ext 2 . ▁Con sequently , ▁ext 3 ▁la cks ▁recent ▁features , ▁such ▁as ▁ext ents , ▁dynamic ▁allocation ▁of ▁in odes , ▁and ▁block ▁sub - al location . ▁A ▁directory ▁can ▁have ▁at ▁most ▁ 3 1 9 9 8 ▁sub direct ories , ▁because ▁an ▁in ode ▁can ▁have ▁at ▁most ▁ 3 2 , 0 0 0 ▁links ▁( each ▁direct ▁sub directory ▁increases ▁their ▁parent ▁folder ▁in ode ▁link ▁counter ▁in ▁the ▁" .. " ▁reference ). ▁ ▁ext 3 , ▁like ▁most ▁current ▁Linux ▁filesystem s , ▁should ▁not ▁be ▁fs ck - ed ▁while ▁the ▁filesystem ▁is ▁mounted ▁for ▁writing . ▁Att empt ing ▁to ▁check ▁a ▁filesystem ▁that ▁is ▁already ▁mounted ▁in ▁read / write ▁mode ▁will ▁( very ▁likely ) ▁detect ▁incons isten cies ▁in ▁the ▁filesystem ▁metadata . ▁Where ▁filesystem ▁metadata ▁is ▁changing , ▁and ▁fs ck ▁applies ▁changes ▁in ▁an ▁attempt ▁to ▁bring ▁the ▁" in cons istent " ▁metadata