KSM is a great idea, much of its abilities are available in Fedora 12. I tried it and I had higher expectations to be honest.

That is not to say that it is no good - its great but there is a bit of a cost analsysis that should be done before implementing it. You dont get something for nothing - and in this case ultimately your offloading the higher memory usage onto the CPU. Depending on your hypervisor setup this might not be such a bad thing of course.

In my somewhat narrow testing of it I found that:-

a) Even with the same O/S images running multiple times the memory I saved was about 5-10%.

b) It effectively used about 50% of one CPU running the feature.

I think that to really see a benefit to this you have to be running a huge hypervisor with a ton of memory and cpus and a lot of guests as there is a plateau which beforehand makes it quite inefficient to use the features seeing as (at least with my results) the payback is less than 10% anyway.

But the IPv4 version appears to be a hell of a lot slower than its v6 counterpart.

In fact i've found v6 runs much faster generally (probably cause so few people are using it at the moment). I use it quite often to download new Fedora distros at max speed.

I personally use qemu-kvm and im quite happy with it. Thats running on a dual core machine with 2G of ram (probably not enough ram though!).

For the KVM stuff you need have chips which support Intels VT or AMDS AMD-V so your processor is the most important aspect. A quad core would probably be suitable too if you can buy that.

For just experimentation usage its a fantastic alternative to VMWare (I personally got sick of having to recompile the module every time my Kernel got updated).

On my box myself i've had about 6 CentOS VMs running at once but frankly there were not doing much most of the time. Ultimately its going to boil down to how much load you inflict on VMS underneath, my experience with it has not been very load heavy so I could probably stretch to 9vms on my hardware which is probably on the lower end of the consumer range these days.

The most important bits are your CPU and RAM. If your after something low spec you can do dual core 2g ram but you could easily beef that up to quad core 8G RAM to give you something you can throw more at.

Oh and Qemu without KVM is painstakingly slow - I wouldn't suggest it at all.

I hope to god nobodies got a ** typo in an old script because that could be troublesome.

Even worse it could be simple enough to ** in error on the prompt.

But some PHP tinkering and you could probably do something to pass comments through spamassassin using a socket or something.

Spamassassin would need updating though to work with content-only data.

Wonder if anyones ever thought of this before?

Cmon Slashdot, your taking the piss now..

Dont know much about it, but it appears to support encryption straight from the transport level with no kludges like OTR.

Looks open source too.