This refers to the time it takes for the head to shift positions to where the requested data is located. This would vary depending on how far away it was at the time. Latency refers to the amount of time the drive has to wait for the data to pass over the head. CLV drives move faster on the outside of the disk and therefore, in those instances latency would be reduced. Perhaps the most popular measurement for CD-ROM performance is access time.
Access time is the speed change time, the seek time, and latency combined.
However, you can't simply add them up, because some of these operation go on simultaneously. Generally faster drives have faster access times. The most important benchmark when it comes to CD-ROM drives is the transfer rate. This refers to the amount of time it takes for you to get the information from the disk into your computer. On standard CLV drives this was easy to figure out.