On Thu, Jan 3, 2013 at 4:54 AM, Lars Heidieker <lars.heidie...@googlemail.com> wrote: > On Thu, Jan 3, 2013 at 12:49 PM, Edgar Fuß <e...@math.uni-bonn.de> wrote: >>> Doesn't this depend on filesystem journaling? >> Can someone please enlighten me? >> Is it safe to use write cacheing on a SATA drive with FFS/WAPBL on it? > > AFAIK it depends on the drive, if it doesn't lie about the command to > flush the cache it's safe. > WAPBL sends such a command on commit.
So I think what you are saying is that WAPBL asks the drive to flush it's volatile cache before the journal update is done? There was talk a while back on some list (I don't remember if it was a NetBSD list) that certain OS behavior (maybe not NetBSD) was flushing cache so often that drive cache performance benefits were essentially negated. So the drive would ignore some of the cache requests which leaves systems using journaling vulnerable. The fail-safe was to just turn off cache completely. Andy
