Subject Re: Virtual Machines, is it realy good enough ? was Re: [firebird-support] Re: Server hardware advice needed
Author Alexandre Benson Smith
Hi Marius !

Em 2/8/2011 05:25, mariuz escreveu:
> The io is sometimes slower when running in VM , think there is one big files that contains your virtual machine and to access it the OS must handle all this huge blob or parts of it (I have one machine with 160G and slows down all the server when i do Linux related compilations, or huge IO operations inside the vm )
> That and the extra layer added by virtualisation will slow down io too
> (that can be solved by virtio if you use kvm-linux)
> What is better for the Database is to create one partition (ext3/4) /data and mount it in the vm /data and start the vm with this new partition , this way the io can be faster than using db inside one big large file (raw partitions are faster)
> QEMU supports a wide variety for storage formats and back-ends. Easiest to use are the raw and qcow2 formats, but for the best performance it is best to use a raw partition. You can create either a logical volume or a partition and assign it to the guest:
> qemu -drive file=/dev/mapper/ImagesVolumeGroup-Guest1,cache=none,if=virtio

I understand that everything is running virtualized, so there is no way
to be as fast as a native, I understand that managing a virtual drive
would add a cost.

I appreciate your sugestions to use native partitions to store the
performance critical files.

But my main question is:
If is that slow, how could one use it on production expecting a
reasonable performance ???

Geoff said about hypervisor, that is a very different beast that the
"desktop" solutions for virtualization... As I said, I just used VMware
a bit and Virtual box for 2 years or so... The only production server
that uses virtualization uses WMWare (I think the most basic version)
and the impression I had is that is unaceptable regarding performance.

From the Geoff post the only conclusion for me is... The guy used the
wrong product, and standard virtualization is not suitable for
production environment.

Your sugestions are very good and I will take a look to see if there is
something similar for Virtualbox

Since I personally use virtualization only on development environment
and the performance is acceptable, I had never look deep into optimizations.

see you !