On Wed, Mar 25, 2009 at 05:32:52AM +0000, David A. Holland 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!). +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?
