The Xen of anwsers

New server update 1

I have given Xen/xVM a try, it works great in Debian, paravirtualized which means there are modules in the guest OS that help communicate with Dom0 to make guest run faster. It is a bit harder to make linux DomU or guess OSes since Solaris doesn't come with ext2/3 support in the kernel or even tools to manipulate the filesystem. But with help of a few people on line I was able to get working quite well. Perhaps one of my readers will tell me how to get ext2/3 tools for Solaris pre-built or I will just have to use them inside a DomU.

I also gave windows XP a try in a DomU that is not paravirtual. It was nice easy install, but was a bit slow, but once you boot it for the first time it gets decent performance in fact for CPU limited actictivies such as google earth, it absolutely flys on this box. I ran the vncviewer on my Sun Ultra 20 with an quattro FX1400 card, and I was totally blown away at how fast it all works. Totally unexpected how well it works given its done over VNC on a network with the application being run in a virtual machine. Use the openGL settings they work great.

Of course the Xen on Solaris hasn't been without a few headaches. Out of the box my mother board was set to use cmdk drivers, for those that don't know what those are, they are the EIDE drivers read slow, especially in XEN and ZFS together. It was really quite depressing seeing the dreadful performance 3-4MB/s per drive when booted into Xen performance was quite good with these drivers outside of XEN. Thankfully someone figured out what was going on and posted the solution. Of course not before I invested a few hours of research trying to find a solution that including tuning zil cache in ZFS. Turns out if you enable RAID on some motherboards it uses the real SATA drivers. On this mother board there is a 3rd option which is to enable AHCI mode, the raid mode doesn't work on mine with Solaris, this change requires booting into single user mode and modifing vfstab, I took the easy way out and reinstalled. I haven't done much testing yet, but the iostat numbers look a lot more impressive, I have seen 2 drivers doing over 50MB/s each simulataneously and yet they were reported as only 90% busy. I can't wait till I order my other 500GB drives and have 2 terabytes of storage and 200MB/s off disk, theroretical performance, currenltly I working in a degraded raidz pool with 2 500GB drives. IO is now good in Dom0 haven't done much testing in my DomU's yet.

The string you want to see in prtconf -vp to know that you are using the SATA drivers.
model: 'SATA AHCI 1.0 Interface'

As to the questions of what I will run in Xen, I will be deploying Windows XP that will be accessed from sunrays, and I will be patching the Windows XP so that it supports multiple users using it at the same time. Given the snappy performance with google earth, I might even be able to use it as a gaming solution at least for older games, that will keep my kids happy. I will also be using debian for some small server tasks. intranet webpage and database, probably mysql or postgres. I really like debian for small jobs, give the server 128MB of ram and it just flies for that kind of thing. I will also be doing some other tests with other DomU's as time goes on.

Paravirtualized Debian realy impressed me that it uses almost no cpu resources when idle, much better than vmware server in my experience. I have been using Debian in a DomU for quite a while I have a shell account that sits on a DomU from contextshift.co.uk, highly recomended hosting company. My shell reports that it has been up for over 4oo days. Untill I investigated Xen, the massive uptime scared me, don't they ever patch the kernel, but now I have to ask was the uptime all on the same server, probably not, Xen includes a DomU migration feature so you can move running systems to another host without a noticible effect on the DomU. I haven't tried it yet. But now that I have used Xen its on my list of things to do.

I may give oracle a try in a DomU but it will be purely for testing. A more likely target for it will be in a zone, that has lower overhead than Xen. For actual deployments I beleve Oracle should run as close to the bare metal as possible to get the most out of it. Since you are paying for it, you should get your money worth.

Here are things I plan to try on Xen as time goes on.

Xen Todo List
- See if Xen and Vmware can play nice in a Dom0 together
- try Vmware in a DomU both with full virtual and paravirtual
- use ZFS snapshots to clone DomU's
- use solaris ZFS iscsi volumes for DomU's see what the impact is.
- migrate paravitualized DomU's from a amd-v enabled machine to a non amd-v enabled proc
- try migrating from a Solaris dom0 to a Linux Dom0 ... no clue if it works I haven't even asked.

I will try and take some pictures this weekend. I will also provide more hardware details as well, such as make and model number of the case and power supply.