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diff --git a/doc/assignment3.md b/doc/assignment3.md index 1864f70..fbdb126 100644 --- a/doc/assignment3.md +++ b/doc/assignment3.md @@ -208,7 +208,23 @@ Your answer for each question should be about 150 words. (100 marks total) 1. What are the factors influencing the selection of a disk-scheduling algorithm? (8 marks) 1. Explain the disadvantage(s) of the SSTF scheduling algorithm. (8 marks) - Starvation + The Shortest Seek Time First algorithm will choose the next cylinder to read + from that is closest to the current head position. This ensures that the + distance that the head has to travel is minimized and allows for access to + nearby data quickly. + + However, if multiple requests are added to the queue that all reside near + each other this could cause other requests that are further away to starve. + + For example, if a request is added to a cylinder near the current head + position. Then a request is added far away from the head position. Then + a larger number of requests are placed that are near the current head + position. This could cause the second request to starve while requests + that came in later get served sooner. If more and more requests continue + to be added to the queue that are deemed to have a shorter seek from + the current head then the program waiting for the second request may + eventually give up or have severe performance penalties. + 1. Explain the concepts of a bus and a daisy chain. Indicate how these concepts are related. (8 marks) 1. What are the three reasons that buffering is performed? (6 marks) |