[geeks] Xen server

[Shannon]

I've been running Solaris as my home server for a few years now and
while it works fine, its rapidly growing outdated and I don't really
like where Oracle is currently headed.

I could do a straight conversion to NetBSD or whatever, but I've decided
instead to do something more interesting and flexible: move all my home
servers to a virtual server.

I plan to use my existing Solaris machine for this: A Dell T105 with an
AMD quad-core and 8GB of RAM. It should be more than enough for my uses
even with 3-4 hosts virtualized.

So... I'm casting about for tips, success and horror stories, etc.

I decided against VMWare because the really neat stuff seems super
expensive and a lot of the other stuff is like Fusion and really
intended for a desktop machine to run some guest OS.

Unless someone has a better idea, I've decided to try Xen.

My basic goals are:

	1)	Be able to run a primary server OS which handles
		basic servers like DNS, mail, and so on.
	2)	Be able to run special case OS installs for software
		that need a certain OS or for isolation.
	3)	Run dedicated servers for things like databases.
	4)	Run other OS for training and experimentation.
	5) 	Be able to migrate or fail-over to another Xen server
		as current server ages or has issues.

I used to run a lot of machines at home, run two of them if I needed
failover or any kind of redundancy, and have several to give me access
to different operating systems.

For a lot of reasons, I just don't want to do that any longer. Its
noisy,  power hungry, and takes a lot of work. Also modern machines are
almost always gross overkill for 90% of my tasks.

Its common for me to go through the pain of a full install of an OS just
to try one program, do work for a single client, or some other things
which is just easier with virtualization.

I've been making do with Fusion on the Mac, but I want a "real" virtual
server for the convenience and also to train myself on it.

Some basic questions:

Dom0 OS: Does anyone have a preference for the dom0 OS? NetBSD seems a
good candidate because its packaged Xen for awhile, but then Linux also
seems to have a lot of support for Xen as do the Linux distributions.

Storage: I won't initially have a file server and so I was musing about
different ways to assign file storage for the domU guests.

	a)	Just let dom0 create virtual devices from files and
		assign those to the doms
	b) 	same as a) but use an LVM to shrink/grow them as needed
	c)	run a file server as a domU and have it provide shared
		storage for all the other domU guests

The T105 will have a boot drive and a pair of matched drives as a mirror
initially, and I was wondering how best to set things up with goals in mind.

One factor in the filesystem question is this: its considered a good
practice to limit the memory of the dom0 to only what is needed to
manage the domU guests. If I limit the dom0 to say 512MB RAM and pin it
to a single CPU, that would possibly have bad consequences it it were
doing the file serving. I can't (yet) find any information on if its
better to use a well provisioned Dom0 for serving files or put that off
on a guest domU which can be more flexibly configured.

Yes I realize it would be much better if I had shared storage on another
dedicated file server but the first go needs to be on a single server.

Not having done it before, I'm wondering what makes migration and
failover the easiest, and so on.

Anyway, step one I had considered was this:

	a) 	get Xen running on NetBSD or Linux Dom0
	b) 	get my current Solaris setup running as first domU
	c) 	then start migrating services off of Solaris onto other
		guests.