[nycbug-talk] dragonflybsd: process sharing/virtual kernels

[Bjorn Nelson]

All,

I was wondering what people think about being able to cluster at the  
OS level.  Matthew Dillon is proposing virtual kernels with caching  
as an easier alternative to their goal of process sharing between  
machines:
http://www.shiningsilence.com/dbsdlog/index.php/2006/09/02/1853.html

The end result will be that you can have two or more machines operate  
as effectively one operating system.  Virtual kernels seem pretty  
similar to the VM stuff that has been heating up lately with vmware  
and xen.  The main difference is that to provide the clustering  
ability, you need to add a component for data synchronization.  Could  
this be built on top of the xen work being added to freebsd?   
Possibly using gated and carp together to take care of delegating the  
network/filesystem resources.

Is this basically vmotion from vmware?  Anyone have any experiences  
in this area?

This looks like this is going to be a show stopping feature in the  
future when choosing an operating system for general serving  
purposes.  I can just imagine many of my fears of hardware redundancy  
evaporating when we get to the point of having failover at the OS level.

The benefit of this is basically what Google has realized with their  
cluster of cheap computers.  You don't have to worry about redundancy  
at the host level nearly as much because a host is no longer a single  
point of failure, and you don't have to worry about accurately  
predicting the hardware required for your application as you can just  
add another host to the pool if it's not fast enough.  Now, it's easy  
to see this and say it but as with all issues it's rarely black and  
white.  You may still want to mirror your OS drives, to lessen the  
effect of the higher rate of failure of disks, and you may still want  
to do some homework for purchasing hardware as at a certain point you  
may have realized that you should have started with a faster base  
system as a building block (decreasing returns due to increase in  
overhead per performance of adding another machine, then again can  
this negated by "weighting" the machines so that faster machines  
serve more?).

What other implications are here?  Will sans be obsoleted?

-Bjorn