Re: [tlug] Xen advice, please

[Curt Sampson <cjs@example.com>]

On Thu, 11 Jan 2007, mcooper wrote:

> True. I was thinking that having all my servers virtualized would make 
> management easier. I would be able to test things out buy just copying a 
> virtual server and screwing it up irrevocably, etc.

Well, apps tend to be fairly independent, so you can just test an app
on another system, too. For example, setting up and playing with a new
DNS configuration, and then copying that config over to your production
machine when you're happy with it, will not affect your DHCP server
configuration one way or another.

> I have only one case that might necessitate a virtual server - our database 
> intranet app. It is PHP4 on RHEL3, and it is built on an outdated version of 
> a very early web framework (one of the very first, years before Rails) in 
> which even the original developer is no longer interested. But we are heavily 
> invested in it, difficult to maintain and modify though it is.
>
> I thought that a virtual machine would be wonderful. If the present server 
> can be replaced with a hosted vm, I can then copy the vm on the same host, 
> test modifications before enacting them, and then make the same modifications 
> on the app if there are no problems.  But perhaps that is asking for luxury, 
> too.

Acutally, that's one case where it could be a necessity. PHP apps often
want different versions of modules, different PHP settings, and even
different versions of PHP. If you don't have the sophistication to know
how to set up several completely independent PHP installs on a single
machine, using a separate virtual server for the app can allow you to
install all of the correct software using standard packaging systems.

cjs
--
Curt Sampson       <cjs@example.com>        +81 90 7737 2974