Belt & Braces

Data storage is like most other elements comprising the IT and communications sector in that development and technological achievement have accelerated in recent times. We chart the development of data back-up and storage and…

Backups have two distinct purposes. The primary purpose is to recover data after its loss, be it by data deletion or corruption. Data loss can be a common experience of computer users. Over 30% of users have lost 100% of their files and information at one time, due to a natural disaster, an accident, or a malicious virus. The secondary purpose of backups is to recover data from an earlier time, according to a user-defined data retention policy, typically configured within a backup application for how long copies of data are required. Though backups popularly represent a simple form of disaster recovery, and should be part of a disaster recovery plan, by themselves, backups should not alone be considered disaster recovery. One reason for this is that not all backup systems or backup applications are able to reconstitute a computer system or other complex configurations such as a computer cluster, active directory servers, or a database server, by restoring only data from a backup.

Since a backup system contains at least one copy of all data worth saving, the data storage requirements can be significant. Organising this storage space and managing the backup process can be a complicated undertaking. A data repository model can be used to provide structure to the storage.

Nowadays, there are many different types of data storage devices that are useful for making backups. There are also many different ways in which these devices can be arranged to provide geographic redundancy, data security, and portability.

The table we have produced showing the evolution of data storage shows, unsurprisingly, that we are in an age where the cloud has become the significant medium and model for many individuals and organisations when it comes to backing up our precious data.

As a SOHO business in my own right we have two principal forms of backup in use; an external hard drive and the cloud – in the form of Dropbox. Both are automatic and my Apple Time Machine HD offers us many revisions of files to recover if necessary. Having had major losses of unrecoverable data over the years we draw an enormous sense on well being from the set up. But we’re small fry, our whole backup is less than a terabyte.

In simplistic terms, the back-up process comprises two distinct steps; a repository model on which to base your back-up strategy and how (more likely, where) to manage the data.

The repository model may comprise an unstructured and ad-hoc set of CDs with minimal information about what data is on them and when the files were backed up. A more sophisticated setup could include a computerised index, catalogue, or relational database.

Regardless of the data repository model, or data storage media used for backups, a balance needs to be struck between accessibility, security and cost. These media management methods are not mutually exclusive and are frequently combined to meet the user’s needs. Using on-line disks for staging data before it is sent to a near-line tape library is a common example.

On-line backup storage is typically the most accessible type of data storage, which can begin restore in milliseconds of time. A good example is an internal hard disk or a disk array (maybe connected to SAN). This type of storage is very convenient and speedy, but is relatively expensive.

Near-line storage is typically less accessible and less expensive than on-line storage, but still useful for backup data storage. A good example would be a tape library with restore times ranging from seconds to a few minutes.

Off-line storage requires some direct human action to provide access to the storage media: for example inserting a tape into a tape drive or plugging in a cable. Because the data is not accessible via any computer except during limited periods in which they are written or read back, they are largely immune to a whole class of on-line backup failure modes. Access time will vary depending on whether the media are on-site or off-site.

Off-site data protection: To protect against a disaster or other site-specific problem, many people choose to send backup media to an off-site vault. The vault can be as simple as a system administrator’s home office or as sophisticated as a disaster-hardened, temperature-controlled, high-security bunker with facilities for backup media storage.

Backup site or disaster recovery centre: In the event of a disaster, the data on backup media will not be sufficient to recover. Computer systems onto which the data can be restored and properly configured networks are necessary too. Some organisations have their own data recovery centres that are equipped for this scenario. Other organisations contract this out to a third-party recovery centre. Because a DR site is itself a huge investment, backing up is very rarely considered the preferred method of moving data to a DR site. A more typical way would be remote disk mirroring, which keeps the DR data as up to date as possible.

A History of Data Storage (Courtesy of Kroll Ontrack Data Recovery)