Technical Report CS0184

Title: A Queueing Analysis of Congestion at Interleaved Storage Systems
Authors: Micha Hofri
Abstract: A popular method to increase the effective rate ,of main storage access is to have it consist of several modulas that may be acessed in parallel. While such an organization usualy results in a net gain in the storage access rate it also creates new modes of congestion at the storage controller. This paper analyzes the processes that describe such congestion - queue lengths and delays - arising in a controller that maintains separate register sets to accomodate the request queue of each module. The various processors attached to the main storage are assumed to generate each memory cycle a random number of such requests: the addresses (i.e. required ·modules) are further assumed to follow a first order Markov chain. Using powerful techniques we derive several descriptors of the congestion and hence of the quaiity of service offered by such an organization. The aim throughout is to produce results in a form that can be readily evaluated numerically in terms of the rich collection of parameters used to describe the system and its use of the main storage.
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