LATENCY
latency is that point between when you send a command and when an acknowledgment get to you. if you try to open any program in your system and you click open that point when you click open and when it finally open up for you to work with is what is know has latency.
this happens even everyday world for example when there is a football match and some from a far studio is trying to call some one in the match venue you will notice that when someone in the studio ask a question or talks it talks some time for someone in the match venue to get what he/she said that point where the person in the studio finish talking and that point when the person in the match venue start to answer is the latency.
1. Network latency
Network latency describes a delay that takes place during
communication over a network (including the Internet). For example, a
slow router may cause a delay of a few milliseconds when one system on a lan
tries to connect to another through the router. A more noticeable
delay may happen if two computers from different continents are
communicating over the Internet. There may be a delay in simply
establishing the connection because of the distance and number of "hops"
involved in making the connection. The "ping" response time is a good indicator of the latency in this situation.
2. Disk latency
Disk latency is the delay between the time data is requested from a storage device system and when the data starts being returned. Factors that effect disk latency include the rotational latency main storage
and the seek time. A hard drive with a rotational speed of 5400 RPM,
for example, will have almost twice the rotational latency of a drive
that rotates at 10,000 RPM. The seek time, which involves the physical
movement of the drive head to read or write data, can also increase
latency. Disk latency is why reading or writing large numbers of files is typically much slower than reading or writing a single contiguous file. Since solid device do not rotate like traditional hard dick drive, they have much lower latency.
Other types of latency
Many of other types of latency exist, such as ram latency (a.k.a. "CAS latency"), central processing unit
latency, audio latency, and video latency. The common thread between
all of these is some type of bottleneck that results in a delay. In the
computing world, these delays are usually only a few milliseconds, but
they can add up to create noticeable slowdowns in performance.
