[xen-tools] Re: [OT?] xen as a base

[Steve Kemp]

On Wed Aug 08, 2007 at 17:23:29 +0200, Anton Melser wrote:

> Hi there, This is probably a bit OT but here we go
> As mentioned, I am hoping to put in place a sort of system for the
> servers we host. Basically, people have a choice - debian or centos. I
> wanted to install straight off a base debian and then just use
> xen-tools to install either debian or centos.

  That sounds reasonable.   Though to be honest I'd probably set
 them up with the "final" operating system by default, or leave them
 blank and let the user do the install via the xen-shell.

  It seems like a waste of time to install Debian then immediately
 replace it with CentOS - even though both installs would only take
 a matter of minutes.  (I'd suggest you do two pristine install, then
 tar them up - and use the --install-method=copy to do *fast*
 installs if you're looking at doing a few guests and you want them
 to be identical and reproducible.)

> So, my question, before I spend ages getting expert on the subject, is
> "what are the really annoying/limiting factors when using a guest as
> opposed to a bare metal install?". Are there lots of gotchas when
> running a centos guest on a debian host? Is this going to end up being
> *more* work than just maintaining bare metal installs?

  I think not.  But it is hard to say.  Certainly for things like
 running sftp servers, and doing little work upon the instances 
 you're not likely to run into too many problems.

  I've easily managed to run 10-20 Xen guests upon a single server
 and that is a huge win from a cost point of view.  Of course if those
 guests must have high uptime/availability you really should look at
 having capacity to move them over - suddenly one failing disk drive
 means 20 machines are down, not just one!

  If you want real "success stories" you might be better posting to
 the xen-users mailing list, at xensource.com. 

  Short of heavy IO affecting all guests upon a machine I can't think
 of any significant downsides to Xen compared to real machines.

Steve
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