S 6.69 Contingency planning and operational reliability of fax servers

Initiation responsibility: Head of IT Section, IT Security Management

Implementation responsibility: Administrator, fax mail centre

Measures for contingency planning and operational reliability of fax servers depend on the volume of material processed over the fax server(s) and the required availability of this service.

As a first step all configuration parameters for the communications cards, operating system and fax server application used must be documented. Whenever the configuration is changed, the documentation must be updated accordingly. Only in this way will it be possible to reinstall a fax server in the shortest possible time in an emergency.

Moreover, data backups should be performed at regular intervals, as stipulated in the data backup policy and the security policy. Backups should not be confined to the data partitions but also cover the partitions on which the operating system and the fax server applications are located.

The fax transmissions stored on the fax server must be backed up at regular intervals. Where permanent archiving of fax data is desirable, this should be performed not on the fax server but on external data media.

One or more conventional fax machines should be held in reserve so that in the event of failure of the fax server or the network it is still possible to send and receive faxes. The number of machines required depends on the volume of incoming and outgoing fax transmissions in emergencies. It is sensible to keep the fax machines which were used prior to installation of the fax server as an emergency fallback.

All other available measures aimed at increasing operational reliability are expensive and should therefore only be considered where availability is very important. Such measures should be considered on a case-by-case basis.

As a first step, the IT system on which the fax server is installed can be equipped with a RAID system. This entails merging several hard disks into a single pool and distributing the data contained on them in such a way as to ensure data redundancy. With RAID level 5, this means that if one hard disk fails no loss of data occurs. However, when RAID technology is used, it has the effect of reducing the overall capacity of the hard disks due to the creation of redundancy. It should also be remembered that this solution is no substitute for external data backups, nor does it protect against total failure of the system.

Operational reliability can also be achieved through the use of several fax servers. If one server fails, the load can be distributed over the other servers. Another advantage of this solution is that the load is split so that the danger of overloading one individual fax server is reduced. On the other hand, any incoming fax transmissions which are located on the failed server will not be available at least for the duration of the failure.

If the availability requirements are such that failures on fax servers can only be tolerated for a matter of minutes, then the use of redundant servers is recommended. For each fax server which is integrated into such a redundancy concept, a second server is then available on which the relevant data is replicated. This solution, if necessary combined with RAID systems, provides the maximum operational reliability; however it is very expensive.

Additional controls:

• Is documentation of the configuration up-to-date?

• Who is responsible for performing backups?

• Are any conventional fax machines available in case of emergency?