Subject: Re: wd, disk write cache, sync cache, and softdep.
To: Daniel Carosone <>
From: Charles M. Hannum <>
List: tech-kern
Date: 12/16/2004 23:30:11
On Thursday 16 December 2004 23:23, Daniel Carosone wrote:
> Finally, it's about getting the most out of cheap hardware - not just
> the most performance but the most reliability as well.

I have to conclude from this that you actually don't understand the real 
problems at all.  To whit:

* You can lose critical file system data (say, the root inode) just by turning 
off the power in the middle of a write.  Fixing this properly really 
*requires* journaling.  As Jason mentioned, your journaling system can take 
care of the write ordering during flushing (and without much performance 

* There are other reliability problems, some of which were mentioned in recent 
(albeit terse) PRs, that are *much* bigger than the risk from the drive's 
write cache.

You're shooting at the wrong target.