November 08, 2008
Looking back: dynamic server appliances with Xen
As Reactrix started deploying the new version of the web application I had been working on, virtualization products like VMWare and Xen were becoming increasingly popular. It seemed like virtualization would be a better way to utilize our server hardware - particularly systems with newer multicore CPUs - and to simplify the process of building and deploying new servers.
We brainstormed with Network Operations to get a better idea of how both groups would like a virtual server environment to work. The gist was that ops wanted to own the base OS and application/host config, and engineering wanted to own the application.
There are tools that make it relatively straightforward to build and update servers in such an environment, and virtualization adds the flexibility that disk images for use by a virtual server instance can be created on-demand. Where a sysadmin might previously have had to drive to the colo and rebuild a disk, a script could accomplish the same remotely with much less time and effort.
As we started prototyping a virtual server architecture, it occurred to us that we might be able to use a mostly read-only runtime configuration. Our production systems were based on CentOS 5.x which already had support for running from a read-only root filesystem using bind mounts for files and subdirectories that really need (or want) to be writable at runtime /etc/fstab, such as /etc/fstab. As an added benefit, the way that CentOS figures out how to mount the filesystems that contain read-write resources for bind mounting gave us an idea for implementing the separation of ownership goal.
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Posted by nickh at 11:38 AM | Comments (0)