Networking

How Linux is taking over the network

Is world domination by Linux a fanciful dream, or could it be a reality in ways we don't expect? Scott Reeves sees the signs.

Is the idea of world domination by Linux as far-fetched as it sounds? Perhaps it is still not deployed on many laptops or desktops worldwide. Does that mean that world domination is a pipe dream? I would argue that it may all depend on whether you define world domination as having it installed on more laptops than its competitors, or whether you define it as being present in more places than its competitors. Linux is used in areas other than the PC world, and it is in those other areas that Linux is stealthily making its advance.

One of the big attractions of Linux is the ability to customise the kernel. In particular, being able to compile for different CPU architectures makes Linux attractive for embedded real time systems. Being able to strip Linux down to the bare minimum amount required to run makes Linux a perfect fit for development of embedded real time operating systems. Which brings me to one point: what exactly is a real time operating system, anyway?

The idea of a real time operating system is that it should have a minimum delay, and a minimum delay variation. The delay variation is known as jitter. The scheduler works on the principal of ensuring processes are run within a certain time. The amount of time spent in a buffer or in memory should be minimised. The overall goal is to minimise the delay and the jitter.

Now consider the architecture of a mid-range to enterprise level Storage Area Network (SAN). A SAN has three main components: storage, switches, and servers. The communication protocol used for communication between these three components is usually Fibre Channel, though Ethernet is starting to provide some competition for Fibre Channel. The market leader in Fibre Channel SAN switches is Brocade, with around 71% of the market share in 2012.  

A SAN switch is a critical part of a SAN. Most Brocade SAN switches shipped use firmware called Fabric Operating System, or Fabric OS for short. Fabric OS is actually a version of real time Linux. If a SAN is using Brocade SAN switches, then Linux is present.  

Logging into a Brocade SAN switch via the CLI will look quite familiar to anyone from a Linux or UNIX background. The login used for various Fabric OS commands is called admin. There are a few Linux commands that admin can run. But mostly, admin is restricted to running zoning related commands. However, the switches do come with a root account. This is occasionally used by field technicians when swapping out components.  

Brocade is probably the big area where Linux is used. Another area is in the SOHO NAS market. There are several NAS devices that use Linux. The Synology NAS, for example, has a Linux kernel. Synology are not the only NAS Company that uses Linux as the operating system. Iomega and QNAP also run a version of the Linux kernel. Apart from being fast and robust, Logical Volume Manager is also included. This means you can (if you wish) use the CLI to do your own volume creation and extension.

There are other areas where Linux looks like it is gaining footholds. For instance, there is the DD-WRT project. This project aims to produce Linux-based kernels to replace the firmware in routers.

The presence of Linux in SAN switches is a big area where Linux has already taken off. Another is in the entry to mid-range NAS market. There are also several types of tape libraries that utilise a Linux kernel. Linux could achieve world domination, but maybe not in the way we expect.


About

Scott Reeves has worked for Hewlett Packard on HP-UX servers and SANs, and has worked in similar areas in the past at IBM. Currently he works as an independent IT consultant, specializing in Wi-Fi networks and SANs.

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