Our first XEN-Experience, a XenServer 5.5 testdrive

As I am in the final week before my holiday and all projects are finished, I thought it might be a good idea to check out the competition. So I downloaded the free version of Citrix’s XenServer 5.5 to see what the fuss is all about.

First I tried to install it on a spare desktop at home (P4 2,4GHz CPU, 2GB RAM) but this failed, probably because the CPU doesn’t supply Intel VT.

Yesterday at work I grabbed two desktops with a Core2Duo E6400 with Intel VT and 4GB of RAM and installed Citrix XenServer 5.5 on it.

The installation is pretty straightforward, much like ESXi, and in about 5-10 minutes you will have a XenServer up and running. The first thing I noticed is that the console is very feature rich. We all know the yellow/gray console of an ESXi server and all you can do is basic configuration tasks like set an IP address, DNS server and default gateway, give the server its name, do a few tests and that’s about it. The console of a XenServer has a lot more features. Next to all ESXi-like features you can start and stop virtual machines, configure storage, resource pools and licensing, configure back-up, restore and updates.

Next step is installing XenCenter the VI client for XenServer. This is very simple and before you know it you have a management tool and you’re ready to add your first XenServer to it. And so I did, I added the XenServer I installed earlier and browsed through the various screens, tabs and settings. The first thing you will notice when you’re used to the VI Client and the vCenter interface is that XenCenter looks very similar but you miss a lot of features and settings. It was like I installed the vCenter or VI Client Lite edition.

At first glance the options I really like are the Power action icons on the Performance tab and the Undock/Redock option on the Console tab.

Next up was installing a virtual machine, so I inserted a Windows 7 RC DVD into my laptop’s DVD player to find that it is not possible to connect the client CD or DVD. I had to insert the DVD into the XenServer DVD player or create an ISO store and upload the DVD. A very big limitation in my opinion.

After a successful and fast Windows 7 installation I also installed a Windows Server 2008 R2 virtual machine and experimented with both. When I shutdown the Windows Server 2008 virtual machine  I noticed a little flaw. After 5 minutes the console kept showing the screen with the text ‘Shutting down…‘ so I thought there was something wrong with my installation until I finally noticed the text above the console screen ‘This VM is currently shut down. Click here to start it.’  Nothing big but when I shutdown a virtual machine I want it power off, this is confusing. A simple screen refresh would have been nice.

After the confusing I decided to try out live migration so I installed a second XenServer and created a 50GB LUN on our Dell EqualLogic SAN. So far so good, but how to get iSCSI working? First we dug through the Admin guide and Anne Jan informed with his friend, Google. He found out that there is really no easy way (GUI) of doing this so we had to detach NICs and configure IP addresses using the command line.

When that was fixed we could connect to our shared storage and we connected it to our first XenServer. No problems, so we tried to move the virtual machine files to the shared storage and because we are using the free version of XenServer we do not have fancy features like storage migration. We had to copy the virtual machines to our shared storage and removed the old files, this takes 20 minutes but it works.

The next step is to perform a live migration so we tried to connect our 50GB LUN to our second XenServer. This FAILED because the LUN was already in use by the first XenServer. With the Hyper-V 2.0 TechNet presentation still in mind we initially thought that XenServer had inherited the same flaw as Hyper-V 1.o, non-cluster aware storage, but this time it was our own fault. XenServer has a more logical location to place shared storage which is to be used in a XenCenter Pool. All XenServers and attached storage which is used in a pool is connected and configured in that pool. So no more configuration of cluster (storage) resources on an individual host.

Finally we could try live migration of a virtual machine to a second XenServer and again it failed. Maybe ‘failed’ is not the correct term, the migration option is just not available, not grayed out, just NOT available. Strange, because all documentation and websites claim that the free version of XenServer does have live migration. Then I notice that the Windows 7 virtual machine did have the ‘Migrate to server‘ option and the Windows Server 2008 R2 virtual machine did not.

So what’s the difference? It turned out that I had not installed the Citrix Tools for Virtual Machines or in short XenServer Tools. WTF? Do I need the XenServer Tools to perform a live migration?

Very, very strange that the live migration support is provided by tools you need to install in a virtual machine. Why? What happens if I want to run an unsupported operating system? We already found out that when you run an unsupported Linux version, you will have to choose between HA or Linux. Does this mean that if I want to run an unsupported operating system, say Linux, I can NOT use HA or Live Migration? Two great virtualization features down the drain! Maybe someone can clear this up for me?

Ok, ok. This article is about unsupported Linux versions on Hyper-V. You may ask why would you run an operating system you know is unsupported? But sometimes you simply don’t have a choice and you will have to virtualize that old server or workstation because the old hardware is about to go up in flames. And ok, the article is about Hyper-V and not about XenServer but I wouldn’t be surprised if the test came out the same. I will certainly test this.

Conclusion: When looking at Citrix XenServer with VMware eyes like mine you cannot help to compare the two and look for XenServer features in VMware places but then I still think it is a product with a lot of potential but for now it still has a long way to go before they can seriously compete with VMware in all areas. Sure, with a customer you will have to asses if all features are necessary but even then the product doesn’t give me the confidence to run a large enterprise environment. But maybe that’s just me and I need some more experience with the product and have a go with the Citrix Essentials pack.

What is really like is the feature rich XenServer console where you can start/stop a virtual machine, configure storage, resource pools and licensing, configure back-up, restore and updates. This is something I miss in VMware’s ESXi, that console is very limited so for virtual machine actions or configuration tasks you will need to access the ESXi server using the VI client.

What I do not like or miss is the option to connect your client CD/DVD to a virtual machine, the lack of iSCSI configuration options in the GUI and the need for XenServer Tools to enable Live Migration.

A test drive with the Essentials Pack is planned after my holiday so check out www.VMGuru.nl and we will keep you posted.