zfsembedsdatadirectlyinalogentry.Forlargeval-ues,itwritesdatatodiskredirect-on-write,andstoresapointerinthelog[21].Thisgiveszfsfastdurabilityforsmallwritesbyflushingthelog,avoidstheoverheadofwritinglargevaluestwice,andretainstherecoveryse-manticsofdatajournaling.Ontheotherhand,btrfs[26]usesindirectionforallwrites,regardlessofsize.Itwritesdatatonewly-allocatedblocks,andrecordsthosewriteswithpointersinitsjournal