On Wed, Jan 23, 2019 at 8:53 AM Michal Soltys <soltys@xxxxxxxx> wrote: > > Hi, > > From kernel documentation: > > "In write-back mode, MD reports IO completion to upper layer (usually > filesystems) right after the data hits cache disk." > > Does "data hits cache disk" mean the actual flush of the journal device as well ? > Or is it staged for later moment when the full-stripe write(s) to the actual raid > device are to be performed ? > MD layer will write the data to the cache disk, but not flush it. Flush happens when upper layer (file system or application) issues flush (fsync, etc.). Does this answer the question? Thanks, Song
