[qmailtoaster] Re: Security

[Eric Shubert]

Jake Vickers wrote:
Phil Leinhauser wrote:
I think you might be talking about vmware in general?  This was mainly
talking about doing snapshots in VM.

  


Yes, I was. That's what you get from a thread-hijacker! ;)


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Hehehe. Yeah, I wasn't very clear on that. My bad.

I wasn't sold on snapshots, but Phil has clarified things for me. They 
are very nice, but you want to leave them off during normal operations.

I do not have a problem with running VMs in production. They do require 
a bit of tuning however. Running them on older cpus that do not contain 
specific virtualization features can result in additional overhead that 
will affect performance.

Jake, I'm guessing here, but virtual guests can/will run with near 
bare-iron performance as long as the workload is primarily in user 
space. When privileged (system) instructions are required, either Binary 
Translation or hardware paravirtualization is required to perform these 
operations for the guest. This would include creating new processes in 
the guest, which I'm guessing is where QMT is taking a performance hit. 
In order to get over that apparent 500 user threshold, I would be sure 
that the host system has a cpu which supports paravirtualization (VT-x 
or AMD-V), that's it's turned on in the bios (not on by default in many 
systems), and that the QMT guest is actually using it (check the guest 
vmware log).

--
-Eric 'shubes'


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