high availability

The interview below is part of our Virtualization Video Series, a recurring theme we want to implement on Virtualization.com featuring interviews with key players from the industry, event reports, etc.

This interview (written transcript below) was recorded at the Profoss 2008 event on Virtualisation and features Werner Fischer, Developer at Thomas-Krenn.AG being interviewed by Toon Vanagt on OpenVZ, high availability and virtualization in general.

WRITTEN TRANSCRIPT
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Welcome Werner Fischer, you are a developer at Thomas-Krenn.AG in Germany and you contributed to the free how-to guide on dealing with High Availability Clustering with regards to the OpenVZ project.

(Editorial note: the free guide can be consulted here)

Yes, in fact we came around OpenVZ and doing high availability clustering two years ago. The main idea behind it is that in the past doing high availability was a rather complex thing because you had to care of all the applications you have on the cluster itself. And so we were looking for a simpler way to do high availability.
There is a great benefit in using virtualization in such a setup, because with virtualization behind a cluster you can simply put all the applications you want to make highly available into a virtual environment and simply cluster the whole virtual environment. You don’t have to take care of all the applications. You simply cluster this virtual resource. You don’t have to think over all the problems you might have with clustering applications only.

Why is it so important to build high availability clusters in virtualized environments?

In fact when it comes down to virtualization you have a lot of benefits, but you also have new dangers behind it. In the past – when you had for example four servers in your setup – and one server went down, you still had three servers up and running. For example it was not that big problem when the database server was down for a few seconds, the mail server was still up and running, the file server was still up and running. But today, in a virtualized environment, when you loose a server, you don’t loose a single server, you loose in fact ten or twenty servers. And that’s also what is important about virtualization today: you have to think about what happens when the hardware fails.

I find it interesting that you documented this for your employer, who then choose to make your How-to guide publicly available. What is the motivation behind this uncommon knowledge sharing?

The reason behind is that we want to spread our knowledge. We at Thomas-Krenn.AG are working for our customers. And our customers want to know what they buy. So it is important for them to know how things work inside. And the good thing with Open Source is that you have the possibility to give the knowledge to the customer. And in fact with our solution we don’t have any drawbacks out of this decision. We have a high test-effort in our solution. We test the implementation on a specific hardware and go to customer and say: “You can use this system. You don’t have to do all the testing again, because we do all the testing in our lab.” And so there is no drawback when we document it and everybody can build it on his own. Because when somebody builds it on his own, he also has to do all the testing. And when it comes to a situation where he wants to use it in a commercial environment, he has to spend so much time and money on testing that it is cheaper to buy our box. So that’s a great deal for both – our company and for users who want to test this technology in their spare time or for a smaller project where they can’t afford to buy a solution.

So Werner, Thomas-Krenn.AG also makes it money in consulting or it just lives on the hardware margins on the boxed solutions?

In fact the solution is running out of the box. So you get a system, you plug it into your data center, go configure the IP addresses and you are up and running. The big benefit is that you can use it within 15 minutes or so. You don’t need a long time until the system is up and running. It is rather fast implemented.

What is your experience with the awareness on virtualization issues at your customers side. Is High availability a major concern or do they ask different questions?

I think today the big question for customers is: “Which virtualization technology should I use in my data center?”. That’s a very important question. In fact most of the customers don’t know yet what is the best solution to go today – because it’s a very fast growing market, and technologies are changing very fast. So there is a lot of time necessary to go to the customer, to communicate with him and to get know what’s the right technology to go for the customer. That’s a very big question today.
When customers don’t know what they should use we go to the customer, we spend time with him, but in the end the customer has to make his decision himself what technology to use. So he needs to spend time on focusing on the technologies which are available today and to make the decision afterwards. In fact there are a lot of benefits with all the different kinds of virtualization solutions that are available today but there is also a lot of time needed to get to know all these technologies and to make the decision afterwards.

What advice do you give your customers, who are selecting virtualization vendors and what existing applications are the typical first candidates for virtualization?

It mainly depends on the application, what is technology the best way to go. If the customer does mainly hosting things, like web hosting (Apache Web server, MySQL stuff) or something like this, often a virtualization technology like Virtozzo, OpenVZ or Linux-VServer is a way to go, because there you have a single kernel running. So you have a very small amount of overhead, and very fast solutions in this area. On the other side when you have different systems, like Linux systems, Windows systems, and stuff like that you have to take a technique which has a hypervisor like VMware or Xen, where you have to possibility to virtualize both – Windows and Linux systems – on a single box.

In which cases does it make sense to recommend the hypervisor approach?

The hypervisor is then necessary when you need to provide different operating systems in the guests. For example if you need to provide Windows, Linux, Solaris, or other operating systems on a single box, then it makes sense to use hypervisor-based solutions. On the other side when you can stick with a single operating system, for example you only need a Linux system providing web services, you don’t need a hypervisor because it adds an amount of overhead. When you simply don’t rely on those features it’s much easier to go with other solutions like operating-system-level virtualization like Virtuozzo or Linux-VServer. There you can put much more virtual environments on a single box than you could do with hypervisors.

Werner, what is the main characteristic and advantage of OpenVZ?

The main characteristic is that you have one single kernel image running on the box, but you have still different, secure virtual environments with their own users, their own distributions for example, their own file systems. So you still have secured environments there, but you have the great benefit that you have only a single kernel running. You are much faster than you could be with a hypervisor. For example when you want to up such a virtual environment you don’t have to initialize a virtual hardware or something like that. You only need to fork some processes and you have a new system up and running within four or five seconds. That’s really a great benefit. Also when it comes to highly available systems. When you have a fail over, you don’t need 30 or 60 seconds to boot up the virtual hardware. It takes only a few seconds and the system is up again.

Who are currently driving the growth in the virtualization market? Is it a true demand from customers or rather vendors trying to ‘sell’ their solutions and still raising awareness on the benefits of virtualization?

It’s really a demand. We have seen in the last months that more and more customers are asking for virtualization technologies. In the past our customers bought our servers to put directly operating systems on the servers. We now also see our customers asking for VMware, asking for Xen, or asking for Virtozzo. So they are aware of these different technologies. Sometimes they don’t know what technology they should use. But we see that virtualization or not just a hype, it’s getting into the data center. More and more customers are asking for it.

Thanks a lot for your time and hope to see you soon!

Thanks. Bye!

More info: HA cluster with DRBD and Heartbeat