David Cary Hart wrote:
On Fri, 2005-11-25 at 13:25 -0500, Matt Morgan wrote:
On 11/25/05, David Cary Hart <Fedora@xxxxxxxxxxx> wrote:
This is an exercise in intellectual curiosity. Do I understand the
concept correctly?
I see two possible applications:
1) Running instances of FC4 and FC5 beta as virtual machines.
Does this make sense?
2) Splitting a server into functional virtual machines. For
example, an instance running postfix, an instance running httpd
and an instance for rbldnsd.
a) Does this improve performance?
b) Is it safe on a production server?
All your examples are possible.
I don't think Xen improves performance in any way. It causes less of a
hit than User-Mode Linux, however.
Think of a small hosting concern. My mate runs three servers, one for
mail, one for web, one for other stuff.
Think one real server, one UPS (or a smaller one, or it lives longer),
one CPU etc,
http://os.newsforge.com/article.pl?sid=05/11/15/1641244&from=rss
Crenshaw said the drive toward virtualization has been further
invigorated by data that shows the average server uses between
15% and 25% of its CPU capacity. Virtualization, on the other
hand, could improve that to 80% or more, "so you can get more
productivity from less hardware," he said, adding that "it comes
down to more productivity at less cost. [You can] take advantage
of faster, better, cheaper hardware more quickly and without
extensive qualification cycles because the software is qualified
to the virtual machine rather than the hardware."
I don't think you'd want to go beyond 80% because if you do
responsiveness will suffer. Even at 80% you'd want to think about an
upgrade.
Speaking of which, xen offers the ability to upgrade with zero downtime:
if my mate set it up properly and he found spamassassin in the
mailserver holding up the web server, he could bring a real server out
of retirement and move the running mail (or web) server onto it.
Read the docs, it's really cool stuff. And, unlike UML, it actually
seems to be an active project. Each time I checked out UML and the past
couple of years I couldn't tell anything useful was happening.
--
Cheers
John
-- spambait
1aaaaaaa@xxxxxxxxxxxxxxxxxxxxxxx Z1aaaaaaa@xxxxxxxxxxxxxxxxxxxxxxx
Tourist pics http://portgeographe.environmentaldisasters.cds.merseine.nu/
do not reply off-list
