Sun is offering new terms for instantly upgradable, capacity-on-demand (CoD) servers. Three years after the concept first emerged, many firms are using such systems but software support remains problematic.

CoD offers access to pre-installed dormant processors to cope with demand spikes or the need to create new partitions. For example, a retailer could switch on extra capacity in December and then decide whether to retain the extra power after the Christmas rush.

Sun and HP pioneered pay-as-you-go plans with high-end servers in November 1999. This month, Sun is expected to expand its reach by letting firms defer some capital acquisition costs and then pay for usage.

This will follow Sun's new Capacity on Demand 2.0 service that extends the plan to mid-range Sun Fire servers. The new version ends security concerns because Sun no longer directly monitors customers' usage. "Providing ways for IT buyers to acquire kit is critical," commented Matthew Keep, Sun enterprise product manager.

Sun said that 40 percent of E10000 buyers activated CoD; IBM said 70 percent of iSeries buyers who had the CoD feature used it. "People said it was the best thing we had done in years," said Ian Jarman, IBM iSeries global manager. "You'll see it on practically all iSeries servers."

However, pricing and technical problems remain. Oracle and others that charge for software usage per-processor have yet to rework tariffs to accommodate temporary usage of chips. Also, capacity-on-demand works best where dynamic partitioning allows users to switch application resources on the fly. Microsoft does not have the capability in its Windows server families.

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