. ▁The ▁size ▁of ▁a ▁block ▁can ▁vary , ▁affect ing ▁the ▁maximum ▁number ▁of ▁files ▁and ▁the ▁maximum ▁size ▁of ▁the ▁file ▁system : ▁ ▁Journal ing ▁levels ▁There ▁are ▁three ▁levels ▁of ▁journal ing ▁available ▁in ▁the ▁Linux ▁implementation ▁of ▁ext 3 : ▁▁ ▁Journal ▁( low est ▁risk ) ▁Both ▁metadata ▁and ▁file ▁contents ▁are ▁written ▁to ▁the ▁journal ▁before ▁being ▁committed ▁to ▁the ▁main ▁file ▁system . ▁Because ▁the ▁journal ▁is ▁relatively ▁continuous ▁on ▁disk , ▁this ▁can ▁improve ▁performance , ▁if ▁the ▁journal ▁has ▁enough ▁space . ▁In ▁other ▁cases , ▁performance ▁gets ▁worse , ▁because ▁the ▁data ▁must ▁be ▁written ▁twice — once ▁to ▁the ▁journal , ▁and ▁once ▁to ▁the ▁main ▁part ▁of ▁the ▁filesystem . ▁▁ ▁Order ed ▁( medium ▁risk ) ▁Only ▁metadata ▁is ▁journ aled ; ▁file ▁contents ▁are ▁not , ▁but ▁it ' s ▁guaranteed ▁that ▁file ▁contents ▁are ▁written ▁to ▁disk ▁before ▁associated ▁metadata ▁is ▁marked ▁as ▁committed ▁in ▁the ▁journal . ▁This ▁is ▁the ▁default ▁on ▁many ▁Linux ▁distributions . ▁ ▁If ▁there ▁is ▁a ▁power ▁out age ▁or ▁kernel ▁pan ic ▁while ▁a ▁file ▁is ▁being ▁written ▁or ▁app ended ▁to , ▁the ▁journal ▁will ▁indicate ▁that ▁the ▁new ▁file ▁or ▁app ended ▁data ▁has ▁not ▁been ▁" comm itted ", ▁so ▁it ▁will ▁be ▁p urg ed ▁by ▁the ▁clean up ▁process . ▁ ▁( Th us ▁app ends ▁and ▁new ▁files ▁have ▁the ▁same ▁level ▁of ▁integrity ▁protection ▁as ▁the ▁" j ourn aled " ▁level .)