[Samba] Possible Issue with Samba Blocking I/O and CPU

[Andy Liebman]

> With this setting of write cache, if the apps have a good locality
> of data reference you'll almost never hit the disk, as everything
> will be served out of that memory cache.
>
> Sorry I can't be too helpful here, but this really doesn't look like
> a Samba problem.
>
> Jeremy.
>    

Thanks Jeremy,

It's not really possible that I could "almost never hit the disk". I am 
writing 80 MB/sec of new data to the storage, and I'm reading 220 MB/sec 
of data from the storage.  Doing this hours on end without any repeated 
data.  The size of this Samba cache is very small compared to all of 
that data.

Since sending my first email, I have another 2 hours of flawless 
performance.  This contrasts with days on end of these "periodic 
dropouts" before we set the "write cache" line.

I realize there might be a kernel issue.  But I want to understand why 
setting "write cache" might mitigate it, and where there is any serious 
downside to specifying a write cache?

Andy