The new Server Core feature in Windows Server 2008 enables Microsoft to compete head to head with open-source Linux as a platform for running Linux and Unix server software.

Windows Server Core is a new text based operating mode in Windows Server 2008 that resembles the non-graphical console used by most Linux server systems.

Server Core systems cannot host the full range of Windows applications, but they can run Microsoft’s Subsystem for Unix Applications (SUA), and thus they could run open-source server software such as the Apache web server and the BIND domain name system (DNS) server software. Both are currently the most widely used option in their respective fields.

In a Microsoft presentation on SUA, Shamit Patel, Microsoft program manager, said SUA runs directly on top of the Windows kernel, “SUA provides infrastructure to run Unix based applications. It is not an emulator, it’s a native subsystem.”

While earlier versions of Windows could run Linux apps using Microsoft Services for Unix, those versions of Windows had a fully graphical environment that required a large amount of RAM. That graphical environment was not required to run Unix applications. In Hypervisor Lab tests, we found a fully graphical Windows Server 2008 system needed at least 512MB, while a Server Core system with SUA could run well using 100MB RAM. This compares fairly well with many Linux servers, many of which are configured with 64MB of RAM.

Server Core also competes with Linux in terms of the purchase price. A single Windows Server 2008 Datacenter Edition license enables customers to have an unlimited number of virtual machines (VMs) running Server Core on a single host server. The Datacenter Edition costs $2,999, which makes the cost comparable to a similar setup of Linux VMs running on VMware ESX Server.

However, some firms consider Windows a poor alternative to Linux and Unix systems because earlier versions of Windows Server had more downtime as they needed to be patched and restarted once a month in order to remove bugs, many of which were associated with the Windows graphical user interface. Microsoft says Server Core systems would need less downtime because it reckons Server Core would need around half the patches of graphical versions of Windows.

Unfortunately this means Windows Server Core systems may still have some way to go before they can compete with Linux in the number of times servers need to be restarted. A Linux system administrator at financial services firm Amicorp told The Hypervisor, “Our servers run a Linux kernel and a single application, such as Apache. We can patch the application without restarting the server, and we rarely need to patch the kernel, so it’s been years since we need to reboot a server because of patching.”