The beauty of virtualisation is that it increases server utilisation. But, the fact is, there is still far too much under-utilised CPU capacity.
As use increases and more applications are virtualised, IT departments then purchase additional servers, and licences to support the new workloads, which increases costs, even though the existing server hardware has not been fully utilised.
The ease with which virtual machines (VMs) can be deployed (spun up) means IT departments may be losing control over licensing costs to cover the operating systems (OS), management tools and applications running across a virtual server infrastructure.
Computer Weekly recently spoke to Mike Madden, general manager, mainframe, at CA Technologies. His job title probably gives away his opinion on the matter of server under-utilisation.
According to CA Technologies, many distributed scale-out platforms are run at under 10% utilisation, and even highly virtualised distributed platforms tend to run at only 50-60% utilisation, whereas mainframes generally run at greater than 80% utilisation.
Running Linux on System z
CA Technologies has produced some data that reveals significant costs associated with running large numbers of x86 virtual machines.
"IBM hardware MIPS [the metric used to meter mainframe use based on millions of instructions per second executed] on the System z [mainframe] is growing. On configurations with less than 1,000MIPS people can go to distributed systems. But we are seeing Z Linux as very cost-effective," said Madden.
Workloads suitable for System Z
- Linux-based desktops
The elasticity of the z/VM and Linux on System z environment ensures that utilisation rates remain high while performance is maintained. Security can be managed directly through the mainframe itself, protecting corporate intellectual property.
- Enterprise applications
Many enterprise applications use per-core licences, so considerable savings can be made by consolidating to Linux on System z, while the high availability of the platform will also minimise downtime to the business.
- Java workloads
Many Java workloads are cyclical and, as such, need to be provisioned and deprovisioned on a regular basis. Linux on System z, running under z/VM, provides an excellent platform for such elasticity, with resource management being a core function of the platform.
- Database workloads
Proven operations, performance management and disaster recovery tools can be applied against the database to ensure optimum performance and protection of the database.
CA Technologies’ virtual machine cost comparison report shows that when using 1,650 VMs, a mainframe system is half of the cost of comparable x86 systems. Far from being an expensive option, the mainframe was found to use less hardware, consume less power, require cheaper IT administration, use lower-cost software licensing, and take up less datacentre space when compared with an x86 environment that would be needed to support an equivalent workload of VMs.
While 1,600 or so VMs may seem a large number, CA Technologies showed that the cost per virtual machine of running 300 Linux VMs on a System z mainframe server was $114, compared with $133 on an x86 system, assuming 24x7 use. At 550 Linux VMs, the difference was even greater: $80 for the mainframe system, versus $112 per VM per month for the x86 system.
Madden pointed out that while the numbers make the mainframe look cost-effective, "general-purpose [mainframe] MIPS are very costly".
A Quocirca paper on optimising Linux on System z commissioned by CA Technologies in 2012, highlighted that the IFL specialty engine IBM sells for its System z mainframe hardware is designed to add additional processing capacity exclusively for Linux workloads running on System z.
In the paper, Quocirca analysts Clive Longbottom and Rob Bamforth noted that IFL provides significant price/performance benefits for customers consolidating workloads to Linux on System z. "The IFL incurs only a one-time charge – as opposed to ongoing monthly licence fees. Additionally, IFL pricing does not count in the normal MIPS-derived [mainframe] software licensing framework," they wrote.
Optimising x86 VMs
Organisations not already running mainframe systems may balk at the prospect of running Linux VMs on System z.
"By cleverly placing workloads on licensed servers in such a way that the overall footprint is minimised, organisations can save millions of dollars in licensing costs," said Andrew Hillier, CTO and co-founder of CiRBA, a software firm that offers virtualisation optimisation technology.
CiRBA’s Software License Control module is an add-on to the company’s Capacity Control Console. It is used to optimise VM placement in virtual and cloud infrastructure.
In recent research, CiRBA looked at 18 virtual environments of organisations with more than 1,100 physical servers. By optimising VM placement and VM density, CiRBA said it was able to demonstrate that those organisations could achieve cost savings of 55.6% on average.
According to CiRBA, if a company takes an environment that is basically random and then concentrates databases and operating systems, it is possible to save 56% over no optimisation.
Hillier said the CiRBA tool was used by a US financial institute to save over $2m in Windows datacentre licensing this year. He added that CiRBA was also able to identify over $13m in additional savings on Oracle datacentre licensing.
Tackle VM sprawl
In terms of software licensing, Stewart Buchanan, research vice-president of Gartner, urged IT directors to consider the impact on licensing costs when they deploy virtual servers.
You need to put controls in place that ensure no more VMs are spun up than the licences you have
Stewart Buchanan, Gartner
Technology such as vMotion from VMware supports live migration, allowing virtual machines to move seamlessly across server hardware. "For instance, if you run Oracle, its partitioning policy does not recognise soft partitioning," he said. This means the customer needs to licence Oracle on every piece of physical server hardware the software could run on.
"You need to put controls in place that ensure no more VMs are spun up than the licences you have," Buchanan added. "Software auditors are very good at catching people out, and can find significant evidence of potential of licence breaches."
Licences based on the number of virtual processes can easily be exceeded if multi-threading is enabled on server hardware. "The smart [IT departments] don’t have one big server farm where any application can run everywhere. They ring-fence the number of server machines the software needs to be licensed for," he said.
Experts agree that virtual machine sprawl will lead to costly licensing bills. Limiting which physical servers applications can run on will lower virtualisation costs. Tools such as CiRBA's Software License Control module can help IT departments squeeze more virtual machines on the same physical server hardware, and for some large businesses, running Linux VMs on a System z mainframe can be cost-effective.