On 30/03/19 13:31, Qu Wenruo wrote: > Hi, > > I'm wondering if it's possible that certain physical device doesn't > handle flush correctly. > > E.g. some vendor does some complex logical in their hdd controller to > skip certain flush request (but not all, obviously) to improve performance? > > Do anyone see such reports? > > And if proves to happened before, how do we users detect such problem? > > Can we just check the flush time against the write before flush call? > E.g. write X random blocks into that device, call fsync() on it, check > the execution time. Repeat Y times, and compare the avg/std. > And change X to 2X/4X/..., repeat above check. > > Thanks, > Qu > > Afaik HDDs and SSDs do lie to fsync() unless the write cache is turned off with hdparm, hdparm -W0 /dev/sda similarly to RAID controllers. see below https://brad.livejournal.com/2116715.html https://queue.acm.org/detail.cfm?id=2367378 -
