Non-linear Seek distance for optimal accuracy of zoned disks seek time in Multi-RAID storage systems

Models of multi-RAID storage systems, implemented on modern zoned disks, are simplified by using an approximation for the seek distance that assumes that the number of sectors per track varies linearly with the cylinder number. Results obtained in this way have matched well against simulation, but the relationship of the number of sectors per track against cylinder number has turned out to be rearkably linear for the specific RAID systems modelled so far. This will not always be the case, necessarily, and in this paper, we go a step further, calculating exactly the seek distance moments, then those of the seek time on zoned disks for specific manufacturer’s specifications. This is to ensure the highest accuracy possible for our model, especially for the non-sequential request streams. The results show good accuracy, even in highly non-linear systems, and indicates a threshold for the model parameters at which the linear approximation becomes unacceptable.