Karim Vaes

What is Grinder?

The Grinder is a Java load-testing framework. It is freely available under a BSD-style open-source license. The Grinder makes it easy to orchestrate the activities of a test script in many processes across many machines, using a graphical console application. Test scripts make use of client code embodied in Java plug-ins. Most users of The Grinder do not write plug-ins themselves, instead they use one of the supplied plug-ins. The Grinder comes with a mature plug-in for testing HTTP services, as well as a tool which allows HTTP scripts to be automatically recorded.

How can I use it? A small tutorial…
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Let’s start out with the basics. Vmware has several products that can be used for virtualization. The most commonly know products are “vmware workstation”, “vmware server” & “vmware player”. They should actually be classed under “emulation” rather than device sharing. In my “hobby environment” I used the VmWare server; It’s free, and it’s solid.

Yet for the enterprise needs, esx is the way to go. Esx is a kernel on it’s own, and enables the virtual machines to really share the resources. This gives esx an extreme advantage over the other products, yet be aware that it also implies technical restrictions/difficulties.

As you can probably guess, adding an extra “emulation layer” will result in some performance loss. Those products will most likely suffice for function test/development environments. Yet a bit more performance and resource sharing is required for servers that need an enterprise production level.

Another thing you need to consider is infrastructure architecture you’re going to build. Here is where the article comes down to… The network sharing part in ALL vmware products is done thru a kind of “virtual switch”. This program is software, and is bound to cpu usage. When several servers share an environment within a vmware product, and one server starts to do a lot of bandwith. Then all servers will notice this as the virtual switch will need cpu power for this.

Don’t get me wrong here… I don’t want to bash the product, but I want to make you aware of this situation so that you can design your server farms for this.
For example: organise your farm so that the intensive servers share their environment with some “light” servers
Also make sure your system architectures know this limitation! This gives them the opportunity to design a system that suits a shared hosting environment. It’s just awfull if everybodies hard work goes down the drain, due to a design issue that could have been tackled.

Check out DNS Pinning explained by Christian Matthies. Didn’t know this was possible… Sometimes I’m truly amazed by the creativity people use to perform malicious actions. Luckily the black- & whitehats remain at the same level (I hope).