Werner Fischer
| Speaker Details | ||
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| Name | Werner Fischer |
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| Title | Developer | |
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Werner Fischer is working for Thomas-Krenn.AG in their development team, where they concentrate on virtualisation solutions and developed a bundled cluster solution based on Heartbeat, DRBD, and Virtuozzo. In his spare time, he uses OpenVZ, also in a clustered environment. After talking to the OpenVZ Kernel developers, they included DRBD directly into the OpenVZ Kernel. Werner has written a cluster HOWTO for OpenVZ, available at http://wiki.openvz.org/HA_cluster_with_DRBD_and_Heartbeat. Before his current job, Werner worked at IBM in Germany and Austria. Together with other IBMers he wrote two IBM Redbooks in the HA and storage area. Werner holds a graduate degree in computer and media security from the University of Applied Sciences of Upper Austria in Hagenberg.
Interview
You'll talk about an High Availability solution you built. Why was it needed?
Traditional HA cluster concepts require a customization of the services which should be made highly available. This is necessary as each of the cluster nodes have its own individual root file system (with its own /bin, /etc, /var, ...), and a shared or mirrored storage (e.g. /data) stores the data for the HA services. So when you want to configure a highly available Apache server, you'll need to configure your httpd.conf in a way that it expects the data within the /data file system. And later on you'll have to manually synchronize httpd.conf between both nodes, as this configuration file sits somewhere below /etc. So we took OpenVZ, and configured OpenVZ as the HA service in the cluster manager. We configured OpenVZ to store its application data (which are virtual environments - VEs) in a DRBD-mirrored /vz partition. The VEs are now FULLY mirrored, so you can easily configure the service you need in the VE, without having the need to further customize the configuration in a special way. This saves time and is less error-prone.
You have developed it for your employer, but all elements are available freely and you even document it. why?
A lot of our customers use Open Source software. Without Open Source software we would not have been able to build such a solution - so we also wanted to give something back to the community with this HOWTO. The solution we sell is a bundle with two Intel-Server (with Areca-RAID-Controllers). This hardware configuration has been extensively tested in our lab, so the customer himself does not need to redo those tests. We also sell Virtuozzo (the commercial version of OpenVZ, which also includes a web-based management) with our solution, and integrated RAID and server hardware monitoring. So it is no problem for us to publish the HOWTO.
Your solution is built with OpenVZ. What are OpenVZ's characteristics and unique features?
To provide a precise answer, I quote openvz.org: "OpenVZ is an Operating System-level server virtualization solution, built on Linux. OpenVZ creates isolated, secure virtual environments — VEs (otherwise known as virtual private servers, or VPSs) on a single physical server enabling better server utilization and ensuring that applications do not conflict. Each VE performs and executes exactly like a stand-alone server; VEs can be rebooted independently and have root access, users, IP addresses, memory, processes, files, applications, system libraries and configuration files." And something I want to add: with OpenVZ you have one single Kernel for both the base system and the VEs. But it is possible to use different distributions in the VEs.
How does it compare to VMWare's servers farms?
VMware provides virtual hardware. This allows you to install different operating systems (like Microsoft Windows, Netware, Linux, ...) in the guest systems. This flexibility of VMware of course adds additional overhead. OpenVZ on the other side does not provide a virtual hardware - only virtual environments (VEs). With OpenVZ, the base system itself and the VEs also share the same, single Linux Kernel. So the performance impact of this virtualization is very small. So when you need the highest possible performance and density, and you do not need different Kernels in your VEs, OpenVZ is a good option for you. When you want to install different operating systems like Windows, Netware, and different Linux Kernels in your guest systems, then VMware or Xen may be options for you.
