Service-Level Agreement

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The service-level agreement (SLA) is a cornerstone of backup and disaster recovery. The service-level agreement defines how much time a service can be unavailable in the case of a disaster (including both hardware and software failures). In doing so, the service-level agreement helps to define the practical requirements to maintain a guaranteed level of service.

At the level of system administration, the SLA defines the maintenance contract with the service provider. For example, the system administrator decides whether it is enough to have assistance in less than four hours or in less than two hours. She also defines the needs for redundant hardware, for example, disk mirroring or a backup server to start if the original one is unavailable.

The same holds true for the administrator of the directory server, who relies on the availability of the system and the system backups from the system administrator. However, it is the responsibility of the administrator of the directory server to maintain the availability of the directory service and the consistency of the data in the directory.

It depends on the organization of the enterprise who exactly in the IT department sets up the service-level agreement and who is the counterpart. However, the existence of such an agreement is important because it determines the decision of how to proceed to guarantee the service level of the directory.

The last but not least point of the SLA is the budget. The higher the availability of your directory services, the higher your costs. To improve availability of the directory server you may think about implementing redundancy. If your management asks you for an SLA of 99 percent, you will have to spend much more money than if you were only offering 90 percent. You have, therefore, a good basis for treating the directory service budget with your management.

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