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Access time is the time between a data request and its provision. Memory latency, seek time, and network latency are types of access time. Hard drives and optical discs have rotational lag, seek time, and transfer time. Bit rate is often advertised as the speed of the drive, making it difficult to determine actual access time.
Access time is the amount of time between a request for data and the moment the data is provided. There are many other terms that refer to access time such as memory latency and seek time. These terms are different for various mediums.
One of the most common types of access time referred to is memory latency. Refers to the amount of time it takes for a memory controller to access and prepare an area of memory for output. This is an extremely important type of latency since it is often the determining factor in how quickly programs can run on a system.
Another well-known type of access time is referred to as network latency. This type of latency refers to the amount of time it takes for a packet of information to travel from one point on a network to another. In terms of Internet access, this time can vary greatly depending on where the package is being sent. For example, the network latency for sending a packet to a computer on the same physical network can be as low as 15 milliseconds, while it can be several seconds if sent to a computer located in a distant country.
Hard drives and optical disc drives have different types of latency. The first is known as rotational lag. Both hard drives and optical discs spin. The rotational delay is the time it takes for the disk to rotate to a position where the read/write head can access the data.
The second type of latency in these types of systems is known as seek time. Once the disk is rotated to the correct position, the read/write head must then move to the correct position to read the data. The time these two processes take is variable and depends on how far away from the original location the new location is.
The last type of latency is known as transfer time. This is the time it takes for the process to transfer information from the drive. This access time is different for various types of drives and is referred to as the bit rate.
With many variables associated with the latency of hard drives and optical disc drives, it can be difficult to determine the actual access time for a given drive. The drives are often advertised for their faster speeds. This count often refers solely to the bit rate of the drive.
