The demand for increased storage performance "is really driven by hypervisors," according to Hu Yoshida, chief technology officer at Hitachi Data Systems. "VMware has taken over like wildfire," he told iTWire.

Mr Yoshida explained that software from companies such as VMware makes it relatively easy to load up a processor in order to make the most of its capacity rather than making do with the relatively low utilisation typically achieved when running a single operating system directly on the hardware.

But running multiple virtual machines (VMs) on a processor increases the I/O load, so it is necessary to improve performance in that area. Furthermore, the operation of multiple VMs means that disk I/O becomes increasingly random - individual applications may read files sequentially, but multiple programs running on multiple VMs on one piece of hardware makes life harder for the storage subsystem.

HDS's approach is to use solid state drives (SSDs) or to stripe data across a larger number of hard drives than would otherwise be required. The company also uses automatic load balancing to deliver the necessary performance.

Closer integration also helps. Mr Yoshida noted that VMware provides a range of APIs that allow it to leverage other vendors' strengths.

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Examples include telling the storage array to overwrite a virtual disk with zeros as part of the formatting process instead of making the VM do the work, or allowing the storage system to move a VM without requiring intervention by the physical CPU.

Yet there are two problems with this approach. Firstly, it is not easy to write code to VMware's APIs, he said. Secondly, storage systems need more powerful processors in order to do the extra work.

However, organisations that previously used virtualisation for tier two workloads such as print and file servers are increasingly using them for their tier one applications, and the offloading of storage functions via the APIs is an important part of getting the performance desired.

HDS is able to virtualise existing storage without requiring a "rip and replace" upgrade to get the benefits of the APIs, said Mr Yoshida.

The company's software for VAAI (vStorage APIs for Array Integration) have been certified by VMware, and "the reaction has been tremendous," he said.

Adrian De Luca, director, pre-sales and solutions at HDS Australia and New Zealand said that according to Gartner's figures, Australia was the largest per-capita user of VMware in the world, and some of HDS's local customers were already using VAAI.

HDS would soon release a plugin that would allow the Hitachi Virtual Storage Platform to be managed from VMware's vCenter software, he added.