Category: Virtualisation

VirtualBox vs QEMU

Turns out that VirtualBox is extremely easy to use for personal virtualisation. I have been using KVM and XEN based virtualisation solutions on the server. They both work wonderfully for that purpose. However, for local machine virtualisation, they are both a chore to setup.

Turns out that another open source product – VirtualBox, is better suited for local virtualisation. I will ensure that it is made available for all my machines in the future. It even supports non-VT based hosts after KVM decided to drop support for it in their recent versions.

I have been setting up some personal virtual machines for the purpose of testing software. It is always a good idea to start off with a virgin machine when doing testing.

I hope that Oracle does not kill this product!

KVM Entropy

I increased the SSL performance further by increasing the entropy pool. I tried following the instructions elsewhere but ran into some problems. While it increased the entropy pool on the host machine, it did nothing for the VM.

So, in order to increase the entropy pool for the VM, I had to enable an extra setting:

RNGDOPTIONS="--fill-watermark=90% --feed-interval=1"

That quickly drove up the entropy pool. The net result is better SSL performance with an improvement of about +30% concurrent connections. I don’t know about the quality of the random numbers but for the purpose of my application, it should suffice.

The only consumer of the random numbers is the SSL. It is only use for ephemeral data transfers. It does not matter if someone deciphers the information because by the time they do, it will no longer be very useful.

Libvirt vs Virt-Manager on Lenny and Lucid

I ran into this random problem with virtualisation recently. For some reason, I just could not manage the LVM storage pools on my virtualisation server from my workstation. My workstation was running on Kubuntu 10.04 and my server was running Debian 5.04 using virt-manager and libvirt on each.

This was a very weird problem because I could access the LVM if there were no allocated logical volumes in them. However, the moment there was anything in them, virt-manager would fail to start the storage pool. This was a really weird problem because I did not have this problem on some of my other installations.

After spending days digging into it, I found out the cause of the problem.

It seems that the libvirt people changed the protocol in version 0.5.0 and swapped the colon delimeter to a comma delimeter. The workstation had a newer version of virt-manager while the server had the older version of libvirt. So, all I had to do was upgrade the libvirt from lenny-backports and that fixed the problem entirely.

The reason why I had not seen this in some other machines is because of the hardware was different. On this particular server, the harddisk was not seen as /dev/sdaX but parked under /dev/blocks/XXX:X instead. So, that is why the confusion with the “:” (colon) came into the picture between the two different versions.

Stress.

Activating XenServer

I have recently been experimenting with Xen after spending a year with OpenVZ. I decided to try out XenServer instead of community Xen because of the commercial support available. XenServer is available for free but with certain limitations controlled by license.

However, I stumbled into problems activating the XenServer license. Turns out that if you wish to activate it, you can use the self-service page that they provided. Unfortunately, that page requires a certain file that can only be obtained by using XenCenter, which only runs on Windows.

It took a few days of looking for information on how to generate that file without XenCenter to no avail till I finally contacted Citrix on their forum and was asked to contact them directly. They told me that they will generate the license for me manually and they will put in a request to make available a non-XenCenter way of gathering the information required to generate the license.

I thought that it was pretty dumb for a virtualisation company to force its users to use Windows. However, since they were nice to me, I would give their product a chance. So, after waiting for a week, I finally received my license in the mail.

The license that they gave me is valid for a year and this buys me time because I think that I will move over to community Xen at some point. I do not wish to go through this hassle of generating manual licenses each year. This brings to mind the whole concept of licensing Open Source Software, which I shall write about later today.

Debian stable comes with Xen 3.2 at the moment while unstable has Xen 3.4, which has many more advanced features while XenServer comes with Xen 3.3. The next version of Debian is due to be released some time this year or early next year. So, I think that once Squeeze stabilises, I will migrate over to community Xen instead.

I think that controlling software distribution through licensing is dumb.