Technology

The use electronic directory services have attained valuable status in recent times especially in the technological legion. Earlier on, around the 1980 s, the directories were based on the main frame as life was simple then. The proliferation of networks which witnessed an upsurge in new networking and messaging systems necessitated the development of the registry system (Coax, xi).

Simply put, a directory service is a software system that keeps, organizes, and offers access to information within a directory. In reference to software engineering, a directory is a map that shows differences in values and names. It facilitates in finding values depending on a name. Just as it is in the case of a dictionary where a name has a variety of meanings, a name in directory may also be associated with different sets of data (Suhanovs, 16-20).

Directories vary in regards to scope. There are those that are narrow and only support a small set of data types and nodes. On the other hand, there are those that are broad and support extensible or arbitrary sets of data or nodes. An example of a broad directory is the telephone one. In a telephone directory, the data items are the telephone numbers while the nodes are the names.   In reference to the DNS, the data items are represented by the IP addresses while the nodes are shown by the domain names. While referring to a network operating system, the resources managed by the OS which include printers, computers, users, and any other shared materials represent the nodes. Since the advent of the internet, many directory services have emerged (Scheil and Huggins, 10).
 
Directory services were an initiative of an Open Systems Interconnection which aimed to get industry players agree on common network set standards in the provision of  multi-vendor interoperability . In the 1980 s the ISO and the ITU developed a set of standards X.500 to be used by directory services. This was to support  network name look  up and  inter carrier electronic messaging . Another system, the Light Directory Access Protocol based on the directory service, X.5000 though using TCPIP stack and a series of encoding of the X.500 protocol DAP was set up giving the needed relevance to the internet (Gregory and Rothstein, 187).

Different vendors have emerged and they offer different implementation options. the ones developed before the X.500 include Domain Name System, this was the first directory service in relation to internet which is still used, Hesiod which was based on DNS was used by the MIT project Athena, The Network Information Service, originally known as yellow pages, was used as a directory service for Unix network. NT Domains developed by Microsoft was used to aid directory services in WEindows machines before the development of Vista. LDAPX.500 implementations include eDirectory which supports multiple architectures such as Windows, Linux and Netware. Red Hat Directory Server which is a commercial product (Scheil and Huggins, 1-10).

The major benefit in using directory services rests on the password management and the users. The directory helps check the number of users and prevents or takes care of the expansion in the number of people using the service. This guides in taking appropriate action regarding migration to new platforms to help serve the users better. The uses of passwords help in the prevention of an un-authorized access to certain information.  Other advantages include authenticity of users, authenticity of resources, right utility of resources and the decreasing of network traffic (Smith and Good, 80-86).
The disadvantages of the directory services are equally considered. The directory services are expensive in reference to infrastructure costs, there is need for adequate planning, and there is complexity in structuring the services for the users (Gregory and Rothstein, 187).

Various technologies are available in mitigating disasters in directory services. However, planning must be done in a way that fits the different requirements of the business in question. Failover clustering is an example of a disaster recovery program. The  Microsoft SQL Server 2000 failover clustering  is made to switch to the failover mode automatically ion case of hardware failure. This program can be used to create a failover cluster for each instance of SQL Server. This program helps a database to automatically switch on the processing of an SQL instance from a faulty server. This program is thus useful if a failure occurs in an operating system or in case there is a planned upgrade on system database resources. The failover program is helpful in high server availability that has almost no server downtime as the clustered nodes must be geographically close. This program may not be useful in disk array failures (Suhanovs, 16-20).

Alternative programs are in abundances and they can be sought in helping in recoveries. Database mirroring is the first alternative of significance. This is a primary software solution to increasing the availability of database. This can only be implemented on a  per data-base basis. It only works with databases which support full recovery modes. Bulk logged models do not support full recovery hence the bulk operations are often logged fully. However, mirroring works with all augmented database compatibility stages.   Other alternatives include log shipping, transactional replication, etc (Scheil and Huggins, 12).