A few years ago IBM pushed Linux on iSeries, now System i, very heavily. Every event had references to Linux, as did much of the IBM advertising. How successful was this and how many of you got into Linux on System i? Well, in my experience, not too many i5/OS and OS/400 users are using Linux for either infrastructure or business applications. Here at Quattro we’ve been running Linux on two of our systems for about four years for a variety of functions, all infrastructure-related though.

Linux is great. I really like it from a technical perspective. It can be challenging to implement some software utilities, but it is very fast and portable. OK, these are not particularly good reasons to rush out and put POWER Linux on to your System i, and they certainly wouldn’t wash with an IT director.

So, should we bother with Linux? As with many things in computing, it depends. Putting Linux on your System i to run infrastructure functions, such as DNS, DHCP, Windows file and print sharing etc, is perfectly acceptable and needn’t use up too much processing resource on your system either. However, I’ve discussed using Linux for infrastructure workloads in a previous article, so I won’t cover it in this article. If you’d like the previous article, then please email me and I’ll send it to you.

What about business applications, though? Well, there are many of these. IBM has recently announced that it has 2,500 business applications which run on POWER Linux and around 15,000 Linux customer engagements worldwide. Another major player in the Linux application environment is Oracle. Many of its offerings run under the Linux operating environment, so can run quite happily on your System i. IBM itself has many applications running under Linux, including Content Manager, which uses DB2 for Linux, and Lotus Domino.

These kind of applications will be more attractive to IT decision-makers and coupling them with the fantastic virtualisation capabilities of System i and i5/OS can make these applications very appealing to organisations. Running an Oracle or DB2 for Linux application in a partition linked to i5/OS providing virtual disk to Linux can provide superb performance, reliability and simplified systems management.

The area of utility partitions is where I believe we’ll really see Linux used on System i. The traditional approach with POWER Linux on the box is to install a partition with Red Hat or SuSE and then install the necessary applications. Utility partitions first materialised with the 3Com IP telephony offering and now the Nortel offering too. That kind of limits us to IP telephony solutions. Don’t get me wrong; this is the way telephony is moving, so it’s great that we can run such an important business function on one of the most reliable and resilient computer systems around.

Recently there’s been another packaged offering which takes us beyond IP telephony – desktop virtualisation. How great would it be to virtualise your Windows/Unix desktops and have the access management running on your System i? Well you now have the opportunity to do that.

Let’s look at how the two Linux utility offerings work on System i. Both the IP telephony (IPT) and Virtual Desktop (VDT) offerings run within a Linux partition on System i. Before we implement a Linux partition, we need to determine a number of factors:

• Ethernet adapters (physical, virtual or both)
• CD/Tape (physical, virtual or none)
• Disk (physical, virtual or both)
• Processor requirement
• Memory requirement
• Capped or uncapped partition.

Quite often Linux/AIX partitions use a combination of physical Ethernet adapters and virtual disks. If the Linux/AIX LPAR needs to communicate with any of the other LPARs on the same system, then we would also set up virtual Ethernet adapters too (see Figure 1).

Assigning virtual adapters to Linux is done via the HMC. This can be done dynamically, whilst the partition is active, or permanently by setting up the virtual adapter requirements in the partition profile. Remember, if you assign resources to a partition dynamically it will be lost the next time the LPAR is started, unless you make the change to the partition profile too.

IPT has built-in application resilience, so should an IPT partition fail or require planned maintenance, the remaining IPT partitions/ systems can take over the workload being handled by the original LPAR. This is great application design but, by using i5/OS, we can enhance this somewhat. If our VDT or IPT partition is using virtual disks provided by i5/OS, which is preferable, then there is a reliance on the i5/OS LPAR being active. If we IPL the i5/OS partition, then the Linux partition ‘loses’ its disks.

One method of overcoming this is to have identical virtual disks in two i5/OS partitions presented to our Linux partition. We can then configure Linux to treat these as a mirrored pair. If we then IPL one of the i5/OS partitions, our utility application in Linux continues to run as it only loses one of the mirrored pair disks.

Using the i5/OS-provided virtual disk in our utility partitions is a good solution because you are in full control of how much disk is available to the LPARs. Both the IPT and VDT functions have varying disk requirements; by virtualising the disks we can create disks to the size required and dynamically add more disk space in the future if required. Not only that, the utility partitions get all the usual benefits of i5/OS disk management too. For example, a virtual disk, Network Server Storage Space (*NWSSTG), is seen by i5/OS as just another object, so it is spread across all the available disk arms in the ASP.

On System p it is common to virtualise physical disk and Ethernet adapters in a utility partition using a function called Virtual IO Server (VIOS). What we’re doing on System i is using i5/OS to provide the VIOS functionality, but with enhanced storage management capabilities. It is also valid to run VIOS LPARs on System i too; you need to ensure you have purchased the Advanced POWER Management utility to enable this functionality.

Both the IPT and VDT solutions use Linux as their base operating system and this sometimes frightens customers as they don’t have Linux skills. With both these applications your exposure to the underlying Linux operating system is minimal, as the administration of the applications is carried out via a browser interface. This is important to the i5/OS base as it allows us to utilise the power and flexibility of POWER Linux on System i without the need to learn Linux operating system tools and command line utilities.

Typically, IP telephony has requirements for a variable amount of disk storage, depending on the amount of voicemails you will store. With i5/OS providing the disk resources to your IPT partitions, you can see how this application can benefit from the speed of i5/OS disks and the storage management capabilities built in to i5/OS. Although I have some knowledge of IPT on System i, I would recommend you contact IBM or Typex for further information on this.

The VDT utility is called Power Virtual Display Client (VDC). This Linux utility partition really does allow you to replace your PC desktops with ultra-thin clients. The VDC terminal allows you to connect keyboard, display, mouse, speakers, microphone, power and Ethernet connections. Basically you replace your PC base unit with the VDC unit.

When powered on the VDC unit connects to a Linux partition running the Power VDC Traffic Agent. The Traffic Agent then creates a connection to the system providing the services you require. If you require a Windows desktop session, then the Traffic Agent will connect to your Citrix, Windows Terminal Server or VMware VDI server emulating a PC desktop. The remote server will send back a Windows log on display to the Traffic Agent which will then forward the display image to the VDC device on your desktop, as shown in Figure 2.

In order to keep a track of your display image the Traffic Agent keeps a copy of this on disk in a Swap partition. Linux normally uses a Swap partition when it needs to page data out of memory. With the VDT solution, the designers have used the Swap partition to store application data, your desktop information. Bearing this in mind, it’s quite important for the performance of the disk subsystem used by the Traffic Agent to be fast and reliable; hence, the reason we would look at utilising i5/OS virtual disks for our Linux-based Traffic Agent partition.

If we have VDC users who only really need to access a 5250 emulation session, then we can configure the Traffic Agent in such a way to make a connection across the System i VLAN from the Linux partition to the i5/OS partition.

Let’s take this a step further. In order to use the Traffic Agent to provide Windows graphical display to your desktop using a VDC, the Traffic Agent needs to create a connection to Citrix, Windows TS or VMWare VDI server using RDP or ICA. What better way to use System i than to have those Intel servers as an integrated server on System x or BladeCenter? The communications between the Traffic Agent on your Linux partition and the Intel-based servers would also run across the System i VLAN and all the disk requirements for the Intel servers and the Linux partition would be provided by i5/OS. Figure 3 shows how this configuration might work.

I think we’re all fairly familiar now with the benefits of IPT, so I thought this would be a great opportunity to introduce you to another POWER Linux-based application which really benefits from the virtualisation capabilities of System i and i5/OS. Desktop virtualisation is a hot topic at the moment because of the huge benefits in cost-savings in power consumption, maintenance and the benefits of centralisation. By utilising Power VDC into a Linux partition, we can make the most resilient and reliable servers in your infrastructure, System i of course, a major component in providing these benefits to Windows, 5250, 3270 and X11 users across your company.

Hopefully, we’ll see more of these ‘boxed’ utility applications for POWER Linux. These applications are not traditional i5/OS workloads, but extend the reach of your System i into your organisation without having to learn Linux. They also have the ability to bring amazing cost-savings to the organisation, adding increased flexibility and usability of the systems to your user community.

Links:

Linux on System i   www-03.ibm.com/systems/i/os/linux/index.html
Virtual Display Client   www.powervdc.com/index_english.html
System i IP Telephony   www-03.ibm.com/systems/i/solutions/iptelephony

Glenn Robinson is managing director of IBM System i Business Partner, Quattro Consulting Limited
You can ask him about this or any other Tech Tip at glenn.robinson@quattroconsulting.co.uk