search for: mc_sync

...rites are sequential" rule of ZFS will make a big difference to the worst-case and average latency here, although obviously the best case won''t change. The "guarantee to physical media" bit is done using msync(3C), which of course results is a call to memcntl(2) passing the MC_SYNC flag. What I''m finding is that, on ZFS, this doesn''t actually synchronously write the passed pages to disk before returning - it returns far too quickly (in a few microseconds) for the vanilla SCSI disk I''m using. A quick prod with DTrace shows the IO happening after the...