KNOWLEDGE in the digital form is power-hungry. With every byte of data written on to a hard drive, more power is required for its maintenance.

The bad news for businesses grappling with this is that data continue to grow relentlessly.

According to research firm IDC, businesses can look forward to a yearly data growth of about 60 per cent.

Coupled with the need for businesses to retain data for a long time, it means an inexorable stockpiling of storage hardware in the data centre.

This not only spikes the utility bills of data centre owners, it means that more expensive data centre floor space and cooling systems are required to cater to growth.

The good news is that feasible energy-friendly storage technologies have arrived. Three eye-catching technologies, in particular, promise wide-ranging benefits that extend beyond eco-friendliness.

The first is called thin-provisioning. This is a technology that lets the IT department allocate more storage capacity to applications than it actually has.

For instance, IT can allocate, say, 500GB to a database application, when in actual fact it has only earmarked 50GB of physical disk space to the application.

Thin-provisioning can get away with duping applications because it knows that applications never consume all the asked-for storage in one go. Hence it suffices to parcel out storage according to the incremental demands of applications. This way, thin-provisioning lets companies buy less storage upfront and spread their storage spending over time.

Less power is needed because there are fewer idling hard drives.

The technology was first brought in by US storage firm 3Pardata Inc, and last May Japanese storage vendor Hitachi Data Systems (HDS) announced the capability in several of its products. Another storage firm that offers the technology is NetApp. Hewlett-Packard (HP) has a technology called Dynamic Capacity Management (DCM), which is similar to thin-provisioning.

"The biggest technology problem for 2007 was maximising existing IT resources," said Suresh Nair, NetApp managing director, Asean. Thin-provisioning lets businesses do just that.

A second eye-catching energy-saving storage development this year can be termed "sleepy disks".

Unlike thin-provisioning, this technology tackles the energy consumption problem head on by seeking out and then putting inactive hard drives to sleep to save on power consumption.

While the concept of powering down idle drives seem obvious, there is huge power-saving potential in this technology because as much as 80 per cent of all data stored by a typical enterprise is ripe to be put to sleep - at least for part of the time. This is non-active, or "nearline", data.

Nearline data - last year's sales records, for instance - is usually stored on the same expensive high-end storage equipment as mission-critical online data. Huge savings can be reaped if they can be segregated and dropped into cheaper storage that consumes less power.

US storage firm Copan Systems and Japanese IT firm Fujitsu are major providers of this technology.

Both sell storage products that feature Massive Array of Idle Disks (Maid), a technology based on the concept of spinning down idle drives. Data Storage Institute (DSI), Singapore's research agency, is also an ardent supporter.

Last November, DSI agreed with Copan to do joint-research on Maid solutions.

A slightly different "sleepy drive" tack was taken by HDS.

Last September it announced a retrofit feature, called Power Savings Services, for a line of mid-range storage platforms.

HDS claims its technology does not incur the performance drawbacks of a Maid system.

The third energy-friendly storage development that made a significant splash last year was data de-duplication, a data-compression technique that can shrink the size of duplicated data 50 times.

It does so by recognising repeating instances of the same data, such as the same file that is attached to several e-mail messages, and then creating just one duplicate copy of it.

There are two facets to de-duplication. It can be applied to disk-to-disk duplication or disk-to-tape duplication.

For reducing power consumption in data centres, disk-based data duplication could become an important technology in the next few years.

Jim Simon, Asia-Pacific marketing director of Quantum, told BizIT that disk-based data de-duplication was a "major opportunity" in 2007.

He singled out a further benefit in data de-duplication that goes beyond being energy friendly and broadens the appeal of the technology.

That is, organisations can now back up data at remote branch offices to a central location over a wide area network (WAN).

They can do so because there is now much less data that needs to be backed up. Previously, this would have needed expensive and high-speed network links.

Besides thin-provisioning, idle drives and data de-duplication, another energy-saving storage technology is virtualisation. This is not a new technology, but it was given a new energy-saving lease of hype last year. For the past five years, virtualisation has proved its mettle in helping businesses reduce storage complexities. This is a technology that can round up disparate storage resources owned by an enterprise and present them as a single entity to applications or users.

Doing so reduces pockets of unused spaces that lurk in local drives. Virtualisation increases efficiency and eliminates redundancies. As HDS CTO Hu Yoshida noted in a corporate blog, both facets are what being "green" is all about - when it comes to storage technologies.