July 10, 2009

"Selectively" Using Linux and Other OS

Although Linux lives in lots of places, quite often it doesn't live alone. One case in point is Four Seasons Heating and Air Conditioning, where Mark Rasmussen oversees a mix of office productivity, VOIP, mobile dispatch, network security, and other applications running on a combination of Ubuntu Linux, Microsoft Windows, VMWare, BSD Unix, BlackBerry, and IBM AS/400.

As IT director at the Chicago-based company, Rasmussen is implementing Linux and the other operating systems selectively, based on which environments make the most sense in light of specific applications.

A major player in the heating, ventilating and air conditioning (HVAC) industry, Four Seasons is frequently deluged by phone calls and service orders, particularly during the heat of summer and the cold winter months.

When he first arrived at Four Seasons in November of 2007, Rasmussen faced challenges that included supporting approximately 320 office and mobile employees, extending the company’s technical infrastructure to over 170 fleet vehicles, and maintaining 99.9 percent uptime of critical systems on a 24-by7-by-365 basis. At the same time, he needed to minimize costs, while accommodating constant yearly company growth of 10 to 15 percent.

In response to these challenges, Rasmussen devised a new IT infrastructure consisting of four aspects:

  • User interaction
  • LAN-based VOIP phone systems
  • Mobile phones, database, and data transfer systems
  • Monitoring.

User Interaction

On the user interaction side, Rasmussen decided to replace an existing Linux Terminal Server Project (LTSP) implementation introduced by his predecessor at Four Seasons.

"I saw the original server as a good idea, but I also identified it as a reliability issue. The original server wasn't documented, and it wasn't standardized. The server was based on a single physical box, which left it vulnerable to outages. So we took what my predecessor had started, rebuilt it from scratch, and virtualized it in the process," Rasmussen recalled.

Where the earlier LTSP server supported about 30 terminal workstations, the newer LTSP infrastructure supports about 45 of them, now in use among the approximately 90 employees who work in the office during various shifts.

The company currently uses VMWare virtualization to support a mix of Linux and Windows OS. "We have standardized on Ubuntu as our preferred Linux distribution.

Now services are divided between multiple virtual servers, so one system failure does not take down services. The virtual machines (VMs) are spread across multiple servers for the same reason," according to the IT manager.

"Within the company, only certain users now have Windows PCs, and only if critical software requires it. When and where possible, users are set up with a terminal machine connecting to a Ubuntu LTSP server. This cuts down on licensing costs, allows easy and finite control, and reduces chances of malware or virus incursions on our network."

For crossplatform communications, Rasmussen is deploying Samba, an open source program that runs on Linux and other Unix systems while also providing file and print servers for Windows clients. All of Four Seasons’ Linux and Windows servers join a Samba domain.

Internet connectivity is provided through a Squid proxy server that runs on Linux and other Unix systems along with Windows. For password control and management, the Squid proxy server authenticates against Lightweight Directory Access Protocol (LDAP), an application protocol for querying and modifying directory services running on the Transmission Control Protocol/Internet Protocol (TCP/IP) protocol.

One of the HVAC's VM servers, which is equpped with LT02 tape drives, is being hosted on Ubuntu, with the core OS running Amanda backup. The other hosting servers run VMWare ESXi, with "no native OS other than the bare bone kernel included with the VM application," he noted.

LAN-based VOIP Phone Systems

For VOIP phone calling, Rasmussen needs to support 52 simultaneous calls with long-term call reporting. Four Seasons’ primary and secondary phone systems are Linux-based Digium solutions based on the Asterisk open source PBX and telephony platform.

"I’ve had good experiences with Asterisk solutions in the past.. However, given our higher peak volumes and uptime requirements at Four Seasons, I opted to augment our internal resources with service contracts for our solution," he elaborated.

Mobile Phones, Database, and Data Transfer Systems

Four Seasons also feels a big need to reliably record work request information and get it into the hands of technicians, who are outfitted with BlackBerry mobile phones.

The company continues to rely on a legacy AS/400-based system for recording all customer requests, as well as for inventory, service billing, warehouse management, and accounting.

"However, some of the greatest issues concern how to quickly dispatch techs to their nearest customers – and how to get service request information into their hands, and resolution information back to us again," Rasmussen added.

To that end, Rasmussen selected an outside vendor named Agilis Systems for mobile resource management software. Service ticket information is now being transferred between Four Seasons’ AS/400 back-end systems and the Agilis software via the XML crossplatform data format. "The Agilis application is presently being hosted at the vendor's site, because it has redundancies superior to those of our internal infrastructure," he acknowledged.

Four Seasons’ dispatch center now assigns calls to technicians through a Web interface. Technicians receive and respond to service tickets on their BlackBerry phones.

The terminal workstations used by most of Four Seasons' office workers are outfitted with Firebird--an open source terminal emulation program for AS/400/iSeries systems--in addition to the OpenOffice.org productivity suite and Firefox browsers. All other end user applications are Web/Java-based..


"Due to the competitive nature of our business, we look for any advantage we can get in identifying network issues," Rasmussen observed. "Our firewall is a open BSD-based server which allows us ready access to network information."

On a separate dedicated Ubuntu server, Rasmussen has set up a Nagios open source program to map and monitor the company's critical systems.

Using Linux Where It Counts the Most

To keep costs down and systems up, Four Seasons is deploying Linux and other OS where they count the most.

In the interest of preserving existing investments, AS/400 is still in use as the company’s platform recording and managing service requests. Meanwhile, Rasmussen has selected BSD Unix rather than Linux as a firewall platform.

"I chose BSD over Linux for this particular application because BSD is a leaner environment, and a wealth of information is available about using this environment as a firewall," Ramussen said. "Plus, I'm guilty of a little bit of, 'This solution has worked for me in the past, so why change it?'"

On the whole, however, Ubuntu Linux remains the IT director's preferred operating system. For greater system reliability and end user support, Rasmussen has expanded and virtualized the original LTSP implementation at Four Seasons.

While Microsoft Windows and multiple other OS are also part of the mix, Windows is used only very sparingly, to support mission critical apps that are not yet available on Linux.

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