In August last year, I wrote a blog about the difficulties of building distributed systems in a post titled, Building Distributed Systems – Defeating the Heisenbugs. The word ‘Heisenbug’ in the title, named after the physicist Werner Heisenberg, refers to the phenomenon of bugs that go away when you look for them. Such bugs are common in distributed systems and can be very frustrating to track down. I know from bitter experience!
I noted that Heisenbugs are much less common in mainframes. There are two principal reasons. First, everything happens inside a single machine, under the control of one operating system instance – and mainframe operating systems are pretty good. Secondly, the systems are delivered as an integrated stack of hardware and software, designed and tested by the vendor. ClearPath systems are outstanding examples.
However, distributed systems are here to stay and will only get more common. One reason is the desire to combine ready-made components which run in different environments. Using a data analytics engine to operate in near real-time on data from a transaction processing system is an example. The results of the analysis can be fed back to the transaction environment to optimise its behaviour. Another reason is the wish to extend an application with components written using widely-available skills but in a different environment – extending a ClearPath application using Windows.Net for instance.
In last August’s blog, I said that fabric-based systems could be the answer to building distributed systems without the curse of the Heisenbug. They provide an infrastructure that supports distributed systems along with the advantages of an integrated stack – a single system, in fact. Unisys has now delivered systems with a fabric infrastructure: first, Forward! by Unisys, supporting Linux and Windows, and just recently a range of ClearPath Libra and Dorado systems.
The new ClearPath systems support a combination of either OS 2200 or MCP, together with Linux and Windows, all running in Unisys Intel platforms, within partitions managed by Unisys s-Par®. There’s not enough space here to describe the systems and their capabilities. A lot of ClearPath documentation is available on Unisys.com. I’d like to look at just two points: the Interconnect and security.
The Interconnect provides the means of communication between the partitions, supporting applications distributed variously across OS 2200, MCP, Windows and Linux environments. Different physical media may provide the connections between the partitions. Memory may be used if they are in the same platform, and a low-latency, high-speed wire connection between partitions in different platforms. The applications are unaware of the media used, so new technology may be introduced without any changes.
The very high performance provided by the Interconnect enables application components in different operating environments (OS 2200, MCP and Windows for instance) to inter-operate in way not practically possible across a network.
Significant systems in the public and private sectors are constantly threatened by individual attackers, criminal gangs and even governments. Security is therefore of the greatest importance. The fabric-based ClearPath systems extend many of the unrivalled security attributes of OS 2200 and MCP to a wider environment.
Three factors contribute to the systems’ security. First, unlike other hypervisors, s-Par® partitioning dedicates resources to a partition, preventing ‘cross-contamination’ between application components in different partitions.
Secondly, Unisys StealthTM is available as an option. It is designed to protect systems by creating secure communities, referred to as Communities of Interest (COIs). COIs only contain the devices and users configured to be within them. No resources outside a COI can access or even see the components.
Finally, all the components are housed within two cabinets. There is no external LAN interconnecting them, which may be vulnerable to misconfiguration or attack, using a sniffer for instance. You can simply lock the door!