I've not installed asterisk on xen with much success, but that was over
a year and a half ago, so things may have improved.
But we do have in production with absolutely no issues freeswitch
running on xen for over 8 months now. We will be decommissioning all of
our asterisk servers as we migrate to a xen based virtualized
infrastructure which is allowing us to reduce from a full rack to a half
rack at 151 front.
Mike
On 03/04/2010 10:51 AM, John Lange wrote:
This discussion really boils down to the difference between
full-virtualization and para-virtualization.
Do a google search for "full virtualization vs. paravirtualization".
One of the things you will learn is that VMWare is full virtualization
and Xen is para-virtualization.
Para virtualization exposes parts of the underlying hardware allowing
the guest OS direct access to some things, chief among them hardware
clocks and timing which is absolutely critical to Asterisk.
Asterisk running on a fully virtualized guest OS is unlikely to run
properly because the clock bounces all over the place. Even just keeping
the proper date and time is problematic on these systems which is why
you are supposed to install "VMWare tools" which helps mitigate these
issues.
On the other hand, my understanding is that Asterisk on Xen runs great.
I believe there is even a commercial product for hosted PBXes that is
based on this though the name escapes me at the moment.
And there Xen kernel modules for Digium cards meaning you install the
Digium cards in the Xen box and then all the virtual machines can access
them just as if they were installed on the local system.
A couple more things to keep in mind:
- there is a massive difference between virtualization installed on top
of an existing OS (such as VirtualBox, Microsoft Virtualization and all
the "free" VMWare products), and "bare metal" virtualization like ESX
and Xen. Bare metal is the only way to go for serious virtualization.
- There are now specially tuned installs of some OSes designed for
virtualization. For example, SUSE has an option for "this is a
virtualized system" which installs all the specially tuned kernel
options which makes a major performance difference.
- And, everything I've said above, while still true, is a bit outdated.
VMWare has recently gotten into the para virtualization game and there
has been _tons_ of work done on the linux kernel in the last couple
years to improve the performance of full and para virtulized systems.
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