1) Number of hops :-
- A large number of hops can increase latency because IP processing is required at each hop, adding to the delay caused at the router.
2) Authentication with a directory service such as LDAP, active directory or NIS :-
- The authentication service must be available on the network, with adequate bandwidth & must have enough resources to accomodate the authentication requests are presented to the servers, increasing latency. Authentication adds to latency only when authentication occurs.
3) Retransmission :-
- Link errors, buffer overflows & flow control mechanisms can result n retransmission. This causes packets that have not reached the specified destination to be resent. Care must be taken when configuring parameters for speed & duplex settings on the network device and the NAS heads so that match. Improper configuration may results in errors & retransmission, adding to latency.
4) Overutilized routers & switches :-
- The amount of time that an overutilized device in a network takes to respond is always more than the response time of an optimally utilized or underutilized device. Network adminitors can view vendor-specific statistics to determine the utilization of switch & routers in a network. Additional devices should be added if the current devices are overutilized.
5) File/directory lookup & metadata requests :-
NAS clients access files on NAS devices. The processing required before reaching the appropriate file or directory can cause delays.
Sometimes a delay is caused by deep directory structures & can be resolved by flattening the directory structure. Poor file system layout & an overutilized disk system can also degrade performance.
6) Overutilized NAS devices :-
- Clients accessing multiple fle can cause high utilization levels on a NAS device which can be dtermined by viewing utilization statistics. High utilization levels can be caused by a poor file system.
7) Overutilized clients :-
- The client accessing CIFS or NFS data may also be overutilized. An overutilized client requires longer time to process the responses received from the sever, increasing latency. Specific performance - monitoring tools are available for various operating system to help determine the utilization of client resources.