title: What is the significance of /queue/rotational in Linux?
body: <p>I was searching to identify the way to detect whether a disk is SSD or HDD? I found that there is a way to detect it. This is by reading the value of  cat /sys/block/sda/queue/rotational? If it is 1 then it is HDD otherwise it is SSD. I was wondering what is this file /sys/block/sda/queue/rotational? Why is it used by kernel? What is this k-object that is maintained by kernel? </p>