Worldwide, over 50 petabytes (5 x 1016 bytes) of data are generated every day that have to be safely stored, economically managed, and quickly and efficiently made available to applications and users when required. In 2004, this steadily expanding data volume amounted to 1.5 exabytes (1.5 x 1018 bytes) - and it is still growing.

One storage heavyweight, for example, is the San Diego Supercomputer Center (SDSC) in the USA, which stores approximately one petabyte of data on hard drives and archives another six petabytes on tape. Another example is the Deutsches Elektronensynchrotron (DESY) in Hamburg (Germany), which generates 100 terabytes of raw data in each experiment. But also in everyday work, hundreds of terabytes of storage volume are generated: The data centre of a local hospital like the Klinikum Oldenburg in Germany, has to deal with 20 gigabytes of data every month in form of electronic patient files.

So it's no surprise that market forecasters are predicting high growth rates for storage solutions. Figures from IDC’s latest market research show: From 2005 to 2008, sales (in USD) of NAS will increase annually by almost 15%, and sales of iSCSI solutions annually by an impressive 170%. At an increase of 785% over the entire period, the data volume for NAS- and iSCSI-based low-cost disk
systems will increase almost eight-fold!.

IDC expects the market share of NAS/iSCSI to grow from 13.7% of sales in 2005 to 30.2% of sales in the year 2008. In terabytes, NAS/iSCSI’s market share will increase even from 24.9% to 42.5%!.

Thanks to more powerful drives with higher capacities, the price per Gbyte of storage will decrease by 30% every year. So while sales in the low-cost disk systems market (NAS/iSCSI) will be growing by 190% annually between 2005 and 2008, the data volume on NAS will be growing by 370%, and that on iSCSI by a stunning 2475%!

DAS, NAS and SAN differ mainly in where they interface with the network.

There are currently three basic concepts for addressing storage:

- Direct Attached Storage (DAS),
- Network Attached Storage (NAS),
- Storage Area Networks (SAN).

De facto, no computer system can do without mass storage – mainly hard drives. But how these storage media are connected has changed drastically over the course of their development