▁ ▁However , ▁files ▁being ▁over written ▁can ▁be ▁cor rupted ▁because ▁the ▁original ▁version ▁of ▁the ▁file ▁is ▁not ▁stored . ▁ ▁Thus ▁it ' s ▁possible ▁to ▁end ▁up ▁with ▁a ▁file ▁in ▁an ▁intermediate ▁state ▁between ▁new ▁and ▁old , ▁without ▁enough ▁information ▁to ▁restore ▁either ▁one ▁or ▁the ▁other ▁( the ▁new ▁data ▁never ▁made ▁it ▁to ▁disk ▁completely , ▁and ▁the ▁old ▁data ▁is ▁not ▁stored ▁anywhere ). ▁ ▁Even ▁worse , ▁the ▁intermediate ▁state ▁might ▁inter s per se ▁old ▁and ▁new ▁data , ▁because ▁the ▁order ▁of ▁the ▁write ▁is ▁left ▁up ▁to ▁the ▁disk ' s ▁hardware . ▁▁ ▁Write back ▁( high est ▁risk ) ▁Only ▁metadata ▁is ▁journ aled ; ▁file ▁contents ▁are ▁not . ▁The ▁contents ▁might ▁be ▁written ▁before ▁or ▁after ▁the ▁journal ▁is ▁updated . ▁As ▁a ▁result , ▁files ▁modified ▁right ▁before ▁a ▁crash ▁can ▁become ▁cor rupted . ▁For ▁example , ▁a ▁file ▁being ▁app ended ▁to ▁may ▁be ▁marked ▁in ▁the ▁journal ▁as ▁being ▁larger ▁than ▁it ▁actually ▁is , ▁causing ▁garbage ▁at ▁the ▁end . ▁Old er ▁versions ▁of ▁files ▁could ▁also ▁appear ▁unexpected ly ▁after ▁a ▁journal ▁recovery . ▁The ▁lack ▁of ▁synchron ization ▁between ▁data ▁and ▁journal ▁is ▁faster ▁in ▁many ▁cases . ▁J FS ▁uses ▁this ▁level ▁of ▁journal ing , ▁but ▁ens ures ▁that ▁any ▁" gar bage " ▁due ▁to ▁un written ▁data ▁is ▁zero ed ▁out ▁on ▁reboot . ▁X FS ▁also ▁uses ▁this ▁form ▁of ▁journal ing . ▁