, ▁reliable ▁write ▁ordering ▁is ▁possible ▁by ▁turning ▁off ▁the ▁disk ' s ▁write ▁cache ▁and ▁using ▁the ▁ ▁mount ▁option . ▁Turn ing ▁off ▁the ▁disk ' s ▁write ▁cache ▁may ▁be ▁required ▁even ▁when ▁bar riers ▁are ▁available . ▁ ▁App lications ▁like ▁databases ▁expect ▁a ▁call ▁to ▁f sync () ▁to ▁flush ▁pending ▁writes ▁to ▁disk , ▁and ▁the ▁bar rier ▁implementation ▁doesn ' t ▁always ▁clear ▁the ▁drive ' s ▁write ▁cache ▁in ▁response ▁to ▁that ▁call . ▁There ▁is ▁also ▁a ▁potential ▁issue ▁with ▁the ▁bar rier ▁implementation ▁related ▁to ▁error ▁handling ▁during ▁events , ▁such ▁as ▁a ▁drive ▁failure . ▁It ▁is ▁also ▁known ▁that ▁sometimes ▁some ▁virtual ization ▁techn ologies ▁do ▁not ▁properly ▁forward ▁f sync ▁or ▁flush ▁commands ▁to ▁the ▁underlying ▁devices ▁( files , ▁volumes , ▁disk ) ▁from ▁a ▁guest ▁operating ▁system . ▁Similarly , ▁some ▁hard ▁dis ks ▁or ▁controllers ▁implement ▁cache ▁fl ushing ▁incorrectly ▁or ▁not ▁at ▁all , ▁but ▁still ▁advert ise ▁that ▁it ▁is ▁supported , ▁and ▁do ▁not ▁return ▁any ▁error ▁when ▁it ▁is ▁used . ▁There ▁are ▁so ▁many ▁ways ▁to ▁handle ▁f sync ▁and ▁write ▁cache ▁handling ▁incorrectly , ▁it ▁is ▁sa fer ▁to ▁assume ▁that ▁cache ▁fl ushing ▁does ▁not ▁work ▁unless ▁it ▁is ▁explicitly ▁tested , ▁regardless ▁of ▁how ▁reliable ▁individual ▁components ▁are ▁believed ▁to ▁be . ▁ ▁Near - time ▁ext inction ▁due ▁to ▁date - st amp ▁limitation ▁Ext 3 ▁stores ▁dates ▁as ▁Unix ▁time ▁using ▁four ▁bytes ▁in ▁the ▁file ▁header