On Wed, Mar 25, 2009 at 08:58:18AM +0000, Andrew Doran wrote: > > Log Message: > > Update the note about sync returning before buffers are written: it is a > > piece of historical behavior, not a current bug. Also, while here, add a > > bit about disk write-back caches and point to dkctl/scsictl. > > Bump date. (first time since 1993!) > > Thanks, however: > > +.Sh CAUTIONS > +Many modern disks contain write-back caches. > +In theory > +.Fn sync > +flushes these. > > This is not true, unless you are using logging (or zfs!).
It should be true; why is it not? Does this need to be moved under BUGS? > +In practice there are many possible ways for this mechanism to go > +astray. > +It is prudent (where possible) to allow a few seconds after syncing > +for everything to settle before e.g. turning off the power. > +.Pp > +It may also be desirable to use > +.Xr dkctl 8 > +or > +.Xr scsictl 8 > +to disable the write-back cache entirely. > > This is wishy washy. It gives the sense that we know there is a problem, but > simply couldn't be arsed fixing it. What do you want to convey? Should we have a list of filesystems and whether they work properly? Crossreferences to mount_foo(8) for all foo? Or should it just contain Kirk's advice, that is, people who care about their data shouhld always disable the write-back cache? -- David A. Holland dholl...@netbsd.org
