number 9

Finally made it to UKUUG at Swansea last Saturday.

The main event for me was Xen. (Admittedly I was sat in the Taliesin ‘cluster roadshow’ all day). It was good hearing from users (Marcus) alongside the Xen team (Ian), to be reassured that it wasn’t hype. They both humoured me when I asked my questions, which was nice of them.

I somehow missed VM migration in Xens feature list (moving entire VMs so kernel data structures move too, so TCP sessions are preserved) – up till now I’ve thought of Xen as a ‘fast VMware’ rather than a natural way to package services for resiting around the network. Another use would be snapshotting a crashing system (of which I have plenty ) and putting the image on ice to debug once the immediate crisis is over – Ian mentioned VM breakpoints being added post 3.0, which would really help here.

Once Vanderpool arrives then there’s also the potential for running linux (or better yet, plan9) like Seti@home as a low priority background VM on public access Windows terminals.

I got the impression there were some issues with running Xen images off an NFS share (loopback locking, etc.), which would mean you’d need a SAN to get the full benefit of it (then you get disk snapshots, which you need for the debug stuff). I’ll run diskless clients in my VMs at home if II ever fancy playing with it.

Inevitably, all the other speakers were compared to Xen.
Poor OpenMosix looked disappointing by comparison: no security, limited platform support, and ( the main showstopper in my book ) the fact that the ‘home node’ of any process is a single point of failure for it, however many nodes you have.

The IBM guy (they have hypervisors in silicon, so it’s old hat to them) was doubtful about how robust Xen is. I suspect the price and GPL factors will make all the difference to its progress.

Anyway, the Powerpoint slides are on their Wiki , have a look.

As an added bonus to the day, Oreilly had a stall. So I got my Rails on faster than if I’d waited for Amazon, at a lower price. The place was crawling with Pythons but there seemed to be plenty of people thumbing through it.

Despite the German guy who seemed to spend all day shouting ‘use plone!’ at interested browsers

UKUUG
is next weekend, and although I can’t spare a whole weekend I really want to catch the Xen talks on Saturday morning.

I’ve been following Xen for about 18 months and to my shame I still haven’t got further than building a dom0 kernel and running that as my desktop for 9 months…

In my defence, my weapon of choice has no dom0 and very sketchy domU support, but NetBSD has been stable in dom0 for nearly a year now, and I’ve had NetBSD around the place since last century.

My main problem has been the lack of a serial console on my netbsd gateway (all my mini-itx boxes are headless as they all live in the front room where there’s no room for monitors).
It’s made upgrading the box very dangerous (every buildworld invariably kills the box ) and dicking about with Xen out of the question.

Adding a serial console to NetBSD:

1. needs a buildworld (see above)
2. is badly documented (rare for netbsd)
3. kills your EPIA boxes (I found this when I tried to install on a new EPIA, luckily. That was when I started using FreeBSD again).

According to the bug report, the bootcode errors are now fixed. But I have a better plan.
I need grub anyway for Xen, and grub does serial consoles fine.

Slight problem was that grub can need a bit of massaging to work with non-linuxes, but that’s no biggy now as the NetBSD/xen howto , bless it, has a section on serial consoles.

(in all honesty, my WRT54G arrived last night, so it’d probably be simpler just to flatten the old NetBSD box and sell it to make glue, but I would like a Xen box and it seems like a good candidate).