Six months on from the launch, Beaverton, Oregon-based Sequent Computer Systems Inc claims it has won 30 customers for its ptx/Clusters high-availability clustering technology, most with several hundred users attached. Digital Equipment Corp’s tight VAX/VMS clustering model is the benchmark to aim for, according to Sequent’s clustering product manager James Fitzgerald: the definition is a shared disk system at normal disk access rates between several autonomous machines that are being centrally controlled, he says. Among Unix companies, Sequent has got the closest towards this model, claims Fitzgerald, IBM Corp being the other main contender. NCR Corp with its LifeKeeper product is also making progress.
Networked distributed computing
But the main focus has been networked distributed computing, which doesn’t provide the same levels of performance or fault-resilience – and it’s in this aspect that the Sequent customers are most interested. Components of the Sequent system include a true fault-tolerant distributed lock management system as an extension to the operating system, and an integrity manager to check that all the nodes are working. The Network Queuing System, which Sequent obtained from the supercomputing world, provides load balancing and dynamic job bidding. Software RAID features and volume management – an extension of the Veritas product – are also included. Ease of use is also an important element, as most failures are still the result of human error. Despite their focus on resilience, a set of Sequent’s customers are planning to extend their clusters beyond this and towards transparent data sharing. They are asking clusters to pull together their existing key databases rather than implementing a full networked database, a task that is still very hard to manage. This movement will be accelerated once Oracle users have made the shift over from Oracle 6 to Oracle7, from where they can extend further towards the Oracle Parallel Server. Another boost will come from the availability of the Forte client-server development environment from Oakland, California-based Forte Software Inc, which is currently in beta test, and which enables developers to build an application as a whole, dividing it up later between clients and servers as they wish. It will mean that customers won’t have to re-write their applications to take advantage of clustering. Sequent may also put the stuff up on its forthcoming Microsoft Corp Windows NT-based boxes. But there are still holes in the Unix clustering model, claims Fitzgerald, the most glaring being the lack of a high-availability shared coherent file system across the cluster. Network File System can provide only weak clustering, while the Open Software Foundation’s Distributed Computing Environment is a very large chunk of code not fully shaken out, according to Fitzgerald, and has a lot of baggage that doesn’t apply to clustering, when you have SQL access right there. Sequent is working on its own implementation, but it won’t comment on any release plans.
