KNOW MORE ABOUT ORGANIZATIONAL ASPECTS OF BACK-UP

KNOW MORE ABOUT ORGANIZATIONAL ASPECTS OF BACK-UP

In addition to the necessary technical resources, the personnel cost of backing data up is also often underestimated. We have already discussed (1) how the back-up of data has to be continuously adapted to the ever-changing IT landscape; and (2) that it is necessary to continuously monitor whether the back-up of data is actually performed according to plan. Both together quite simply take time, with the time cost for these activities often being underestimated. As is the case for any activity, human errors cannot be avoided in back-up, particularly if time is always short due to staff shortages. However, in the field of data protection these human errors always represent a potential data loss. The costs of data loss can be

enormous: for example, Marc Farley (Building Storage Networks, 2000) cites a figure of US$ 1000 per employee as the cost for lost e-mail databases. Therefore, the personnel requirement for the back-up of data should be evaluated at least once a year. As part of this process, personnel costs must always be compared to the cost of lost data. The restoration of data sometimes fails due to the fact that data has not been fully backed up, tapes have accidentally been overwritten with current data or tapes that were already worn and too old have been used for back-ups. The media manager can prevent most of these problems. However, this is ineffective if the back-up software is not correctly configured. One of the three authors can well remember a situation more than ten years ago in which he was not able to restore the data after a planned repartitioning of a disk drive. The script for the back-up of the data contained a single typing error. This error resulted in an empty partition being backed up instead of the partition containing the data. The restoration of data should be practised regularly so that errors in the back-up are detected before an emergency occurs, in order to practise the performance of such tasks and in order to measure the time taken. The time taken to restore data is an important cost variable: for example, a multi-hour failure of a central application such as SAP R/3 can involve significant costs. Therefore, staff should be trained in the following scenarios, for example:

• restoring an important server including all applications and data to equivalent hardware;

• restoring an important server including all applications and data to new hardware;

• restoring a subdirectory into a different area of the file system;

• restoring an important file system or an important database;

• restoring several computers using the tapes from the off-site store;

• restoring old archives (are tape drives still available for the old media?).

 

The cost in terms of time for such exercises should be taken into account when calculating the personnel requirement for the back-up of data.

Storage networks and intelligent storage subsystems open up new possibilities for solving the performance problems of network back-up. However, these new techniques are significantly more expensive than classical network back-up over the LAN. Therefore, it is first necessary to consider at what speed data really needs to be backed up or restored. Only then is it possible to consider which alternative is the most economical: the new tech-

niques will be used primarily for heavyweight clients and for 24 × 7 applications. Simple clients will continue to be backed up using classical methods of network back-up and for medium-sized clients there remains the option of installing a separate LAN for the back-up of data. All three techniques are therefore often found in real IT systems nowadays. Data protection is a difficult and resource-intensive business. Network back-up systems

allow the back-up of data to be largely automated even in heterogeneous environments. This automation takes the pressure off the system administrator and helps to prevent errors such as the accidental overwriting of tapes. The use of network back-up systems is indispensable in large environments. However, it is also worthwhile in smaller environments. Nevertheless, the personnel cost of back-up must not be underestimated.

This chapter started out by describing the general conditions for back-up: strong growth in the quantity of data to be backed up, continuous adaptation of back-up to ever-changing IT systems and the reduction of the back-up window due to globalization. The transition to network back-up was made by the description of the back-up, archiving and hierarchical storage management (HSM). We then discussed the server components necessary for the implementation of these services (job scheduler, error handler, media manager and meta- data database) plus the back-up client. At the centre was the incremental-forever strategy and the storage hierarchy within the back-up server. Network back-up was also considered from the point of view of performance: we first showed how network back-up systems can contribute to using the existing infrastructure more efficiently. CPU load, the clogging of the internal buses and the inefficiency of the TCP/IP/Ethernet medium were highlighted as performance bottlenecks. Then, proposed solutions for increasing performance that are possible within a server-centric IT architecture were discussed, including their limitations. This was followed by proposed solutions to overcome the performance bottlenecks in a storage-centric IT architecture. Finally, the back-up of large file systems and databases was described and organizational questions regarding network back-up were outlined. This chapter ends our consideration of the use of storage networks. In the remaining three chapters we concern ourselves with management of storage networks, removable media management, and the SNIA Shared Storage Model.