Almost since the birth of modern, computerised business systems, one of the most critical issues has been the backup, storage and retrieval of important data. Tape, the preferred medium in those early days, was chosen because it was significantly cheaper than hard disk storage options.
However, as the price of disk-based memory fell, so solutions using disk technology gained in currency. One of the reasons for their ready acceptance was the speed at which they were able to execute data storage and retrieval tasks – especially when large volumes of data were involved.
Tape stores data in a linear fashion, exacerbating the process and expanding the ‘window’ for this activity well beyond that required by disk systems. The recovery phase is similarly slow. Users are forced to start at the beginning and run through all the tape in each stored cartridge until the data searched for is found.
On the other hand, disk-based software can take a complete image of the corporate computer system – reflecting all its settings and applications – at the moment of backup. This is known as a snapshot. The restore is equally fast.
Faced with these challenges, tape gradually faded into the background and into the mosaic of outdated technologies.
Until now. Tape is once again stepping back into the data storage environment as organisations find increasing numbers of reasons to backup to the medium once again.
In its new role, tape sub-systems and tape libraries are complementing disk systems in what are known as disk-to-disk-to-tape (D2D2T) solutions which combine the best features of both disk-based and tape-based storage in a single, comprehensive data protection offering.
In such a solution, daily data backups are automated and optimised using disk storage – which also provides instant access to data when a ‘fast restore’ is required. Mature data, on the other hand, is copied to tape storage in off-site tape libraries for security.
Disk based storage allows for snapshot data replication, meeting the demands of today’s IT managers who are tasked with meeting strict service level agreements (SLAs) which include Recovery Time Objectives (RTOs) and Recovery Point Objectives (RPOs).
Essentially RPOs and RTOs dictate how quickly lost data must be recovered and from what point in time the recovery must take place. These are determined by the importance – or criticality – of the information to the business.
However, while speed might be a criterion for fast backups and recoveries in business today, the cost of hard disk storage is still prohibitive for the archiving of non-critical data for long periods of time. It is still far cheaper to have a large library and many tapes for long term storage than massive disk systems.
The tape library thus returns in a new role – as an archival/ long term retention/ recovery tool. It has also gained a significant advantage over disk in this role because it is ideally positioned to meet modern legal requirements compelling public companies to archive every email, memo, invoice and document they ever produce.
Because it’s no longer possible to shred documents or delete data at five or 10 year intervals, the vast volumes of data that need to be archived are best stored on tape, off site. The companies may never look at these archived items again, but they have to be kept secure.
In this light, tape’s ability to provide a simple, cost-effective solution to off-site copy requirements is a key advantage. And should a disaster destroy all the IT equipment at the company’s primary site the tape-based data is retained safe and secure.
At the other end of the market, in smaller business environments, tape continues to play a timeless backup role.
In this arena, budgets for sophisticated disk-based systems and snapshot technologies are unavailable. At the same time, there is less emphasis on strict RPO and RTO objectives, so tape libraries remain a popular solution.
by Kevin Falconer,