ZFS has both a time-based and size-based limit. IIRC the default is 15 seconds and lower of 2GB and some % of system memory. Though in ZFS' case it's not reall

ZFS has both a time-based and size-based limit. IIRC the default is 15 seconds and lower of 2GB and some % of system memory. Though in ZFS' case it's not really a regular write cache as such, as it's used to minimize updates to its on-disk copy-on-write structure.