Effects of Scattering Write Request Arrivals on SSD Performance

Intensive researches have been conducted to reduce the amount of I/O requests to NAND flash memory and to improve the performance of solid state drives (SSDs), by serving some of the I/O requests through the buffers. However, improving the performance by changing the arrival time distribution of I/O requests has not received much attention. Actually, it is possible to arbitrarily adjust the arrival time of write requests through the inside buffer. Therefore, this work evaluates the effects of the arrival time distribution of write requests on the SSD performance by varying the arrival time distribution based on actual server traces from uniformly distributed patterns to more concentrative patterns. As a result, it is found that the average response time of I/O request increases significantly as multiple write requests are generated simultaneously even if the total amount of write requests and the average inter-arrival time of write requests are similar. The founding suggests that not only the buffer hit ratio, but also when dirty buffers are flushed is an important factor affecting the performance of SSDs.