Re: Does mfi write-back cache work for anyone?

[Manuel Bouyer <bouyer%antioche.eu.org@localhost>]

On Thu, Jan 10, 2013 at 01:06:45AM -0500, Thor Lancelot Simon wrote:
> On Thu, Jan 10, 2013 at 12:55:45AM -0500, Thor Lancelot Simon wrote:
> > 
> > I think something still *must* be wrong with the driver -- here is what
> > I see, including output from the Linux MegaCLI utility, which is pretty
> > sure the battery is just fine:
> 
> Thinking about it -- it's almost as if the adapter firmware starts
> up requiring confirmation from the OS that the battery is good and
> that it should run the cache WB.  Like we're missing some kind of
> acknowledgement or something.

I've never had problems like that ...

> 
> Offhand, I don't see any code like this in the Linux driver, but I
> will dig a little harder.

I've not seen anything like that either.

> I'm also wondering whether it might be
> feasible to reverse engineer a few of the battery related megacli
> ioctls and just put them in the kernel.  By using the cache mode
> override we could manage WB/WT on the cache "by hand" if we had
> to, if we detect the adapter doing the wrong thing when the
> battery is actually good.

I'm not sure it's a good idea anyway. If the adapter has disabled the
write cache because it thinks the BBU is not useable, it may still
fail to use the BBU on power failure if the cache is forced on.

-- 
Manuel Bouyer <bouyer%antioche.eu.org@localhost>
     NetBSD: 26 ans d'experience feront toujours la difference
--