[wplug] Windows clustering using VMWare and openMosix ... (theory)

[Patrick Wagstrom]

On Fri, 2004-10-01 at 11:57, Chris Romano wrote:
> > So I got the bright idea of trying something like this once.  The short
> > is that VMWare doesn't like OpenMosix.  It's got some hooks into the
> > kernel to allow it to do some of the stuff and they don't seem to play
> > well together.  I only spent a few hours on it, and afterwards got too
> > annoyed with it, so it might be possible, but I'm thinking no.  Another
> > fact is that some processes in OpenMosix don't migrate well.
> > Specifically process that need lots of disk access.  
> 
> Like a database ...

Umm, close but not exactly.  The difference is in the way that disk
accesses are done.  DB software is highly tuned to access the disk in
particular and predictable ways.  Heck, Oracle even has it's own file
system to help optimize this.  Meanwhile, with VMWare it just creates
one large file.  The actual VMWare process has no knowledge of what it
is writing to the "disk" (actually just a big file).  It could be memory
swap, it could be data, it could be system files.  The point is that the
writes can go anywhere in the "disk" at any time and VMWare has no way
of knowing it.  This is one of the reasons why VMWare's disk performance
is so poor.

--Patrick