Traditional backup sessions may be wholly redundant if you use either online vaulting or CPS - continuous protection - systems. That means whole swathes of tape-based backup technology, including backup software, tape drives, autoloaders and tape-based backup procedures, could be as useless as punched cards and paper tape.

Ironically, medium enterprises and small business could have better data protection than very large business, where the tremendous cost advantages of tape media compared to disks means they cannot afford to move from tape libraries to disk-based protection.

The thinking is that backups are done periodically so that if disks crash you can recover all your data, except any input since the last backup. Backups took time and were disruptive so you couldn't backup all your data. Backups are also written in a single sequential file to sequential access tape, meaning that restores take a long time.

With disk-based backup then restores from the backup container file on disk take place at disk access speed. But you may well ask, why have a backup container file on disk at all? Backup vendors will say it's faster to write a single container file to disk than multiple folders and their constituent files.

But this is only true if you maintain the traditional backup session, run every day or every few hours. Why on earth should you do that? It's a consequence of using tape-based media and tape-based backup software. If you use disk-based media then why should you use tape-based backup software?

Certainly, you get faster restores and much faster backup but you still get what TimeSpring calls a 'protection gap', the period since the last backup when any new data is lost if your server crashes. So - why not backup continuously by quasi-mirroring or continuous snapshots? Disks are getting cheap and a single CPS server could backup several application servers.

Recently Techworld has mentioned several disk-based backup systems, which are all, in EMC CEO Joe Tucci's phrase, 'game-changers'. Here they are:-

Iomega's REV autoloader substitutes 35GB capacity REV removable disks for tapes in an autoloader. It still operates in the traditional backup scenario but is the first disk-based autoloader.

Iron Mountain's Electronic Vaulting continuously copies changed file blocks in a compressed and encrypted form across a network to a manager and secure electronic vault on disk. Restore is via a Windows Explorer-type interface and backup of desktops, servers and notebooks is unobtrusive and secure and fast.

Revivio's Continuous Protection System timestamps and copies changed disk blocks to a networked repository. Restores can be down to minute-level granularity and fault-tolerance is provided.

TimeSpring's TimeData copies file-based changes from Windows servers to a Windows-based repository run by its TimeData software. Protected servers 'see' a networked T: drive for restores.

There are also the Overland Storage and Quantum disk-to-disk-to-tape or D2D2T systems with disk buffers or caches in front of tape libraries, or standalone if you want, with Overland's Reo system.

Disk is still more expensive than tape when you are purchasing hundreds and thousands of reels a year. BUt the trend is for disk prices to fall possibly, if not probably, faster than tape prices. It may only be a year or two before we see disk-based libraries being positioned to compete with entry-level tape libraries.

For non-tape library-using enterprises it is going to become increasingly hard for tape-based protection vendors to explain why their customers should lose data in the 'protection gap' that use of their products with traditional backup software produces; not forgetting justifying the slow restores too.

It could be that we are entering, to use a dreadful marketing cliche, a paradigm shift in data protection procedures.