Running more than one server OS in a data center enables users to work with systems of their choice, but it also creates management challenges.
Configuring and maintaining different systems can be complex and time-consuming. System administrators have access to a plethora of vendor and third-party tools that lessen the burden.
The first step in supporting a heterogeneous data center is to configure the server to support multiple operating systems. Administrators can either rely on hardware sequestering, or mask lower-level idiosyncrasies with a virtualization layer.
Give 'em the boot(s)
Multi-booting is a common technique for companies running multiple server operating systems. The system administrator independently installs different environments on multiple physical disks or logical disk partitions. Then, the sys admin selects the preferred OS from a menu that appears when they boot the system.
To set up a multi-boot system, create a separate area on the disk for each environment. This typically involves dividing a single hard disk into multiple partitions. Each server's hard disk has a Master Boot Record (MBR) that contains a partition table, which specifies how to separate the disk into logically distinct areas.
When the system boots, the basic input/output system looks for a suitable boot device, reads the disk's MBR and executes a small amount of code. The boot code examines the partition table to determine which one is active, then loads the information -- the volume boot sector -- at the beginning of that partition and executes it, transferring control to the OS loader.
Windows has built-in capabilities for managing disk partitions.
Third-party products, such as EaseUs Partition Master, MiniTool's Partition Wizard, and Aomei Technology's Partition Assistant automate the process. Typically, these products delete any existing Windows partition and then create new partitions in your specified sizes.
The second OS will likely be a version of Linux. Two boot loaders, LInux LOader and Grand Unified Boot loader, perform a function similar to MBR.
If a company runs Unix, vendors such as HP, IBM, and Oracle include partitioning functions in their system administration product lines. Parted Magic LLC offers an eponymous tool, Tenorshare makes Partition Manager, and there are others available.
Once you set up multiple partitions on the hard disk, determine where to store company data. Often, admins want to centralize data rather than associate it with an OS. To do this, set up an additional logical partition for the data.
- The booted OS sees the contents of other logical partitions if they are formatted using a file system that the OS understands. If the company wants to hide partitions from one another, it's possible for tools to change the partition table.
Partitioning has downsides. The more partitions created, the more items there are to manage. Figuring out how much space to partition can be a challenge as applications fluctuate in their system requirements. It takes time to add space to partitions after they're created.
Host in a VM
A different approach to hosting multiple environments on a server is to run them within VMs. Virtual machines allow computers to emulate a complete hardware environment within its software. While running one OS, the administrator can fire up a VM just as if it were another application.
Virtual machines run multiple operating systems side-by-side and concurrently. Since each VM has its own IP address and virtualized network connection, a small network of computers arise within a server. Admins can perform the same tasks on the guest servers as with a host, such as run programs, share files and partition drive space.
The disadvantages include reduced speed -- a consequence of emulating hardware with software -- and the additional cost of the VM software -- usually from Microsoft or VMware.
Once a company configures servers, updates occur regularly. Microsoft provides Windows Server Update Services (WSUS), which is automatically installed on Windows servers. Security updates can be distributed and managed via the administrative console. Server admins can also get updates from Microsoft Windows Update, with automatic update downloads from Microsoft. You can alternatively turn it off and check for updates periodically.
Unix systems include a similar capability. For instance, Oracle Enterprise Manager Ops Center reduces the complexity of updating a large number of systems, standardizes the update installation process, minimizes downtime and enables an admin to choose the level of automation.
Upgrading Linux can be challenging, especially if the data center uses multiple Linux distributions. While the OS is designed to be consistent among distributions, nuances exist. Consequently, the user is often tied to the distribution vendor's update tools.
About the author:
Paul Korzeniowski is a freelance writer who specializes in data center issues. He has been writing about technology for two decades, is based in Sudbury, MA and can be reached at [email protected].
Windows and Linux are common operating systems for data center servers. Which one you choose depends on administrator skills, cost, and other factors.