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

[Okan Demirmen]

On Sun 2006.09.03 at 11:02 -0400, Bjorn Nelson wrote:
> 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?

Not really vmotion. vmotion allows one to move a vm instance in realtime
to another node in the vm pool. It works well, though it is limited to
windows.

However, vmware's DRS (distributed resource scheduler), is closer to
what you are refering to, which I don't have access to.

> 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?

sans obsoleted? i don't think so - i think they become more important.