The development of an error budget must start with the identification of the read/write system parameters and how they are influenced by each sub-system in the drive. The read/write characteritics of the media are crucial to the read/write system and represent the most significant portion of any budget. Thus, the performance of the media must be modeled and the read/write chain designed to track any related disturbances. Presented are analytical techniques that can be applied to evaluate any budget and determine performance requirements. An example of budgeting and evaluating performance of a typical conceptual implementation is given within this paper. The budgeting of errors in any system should start with a block diagram of the system of interest and qualitative identification of error sources. For this paper consider the block diagram of an optical read/write system given in figure Before identification of error sources can be done. the mechanisms of the read and write processes must be understood.