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A simple scenario , I have implemented a Email server for my users to access / send emails . Now the users have grown and my server is not able to handle the load .

Now the question is why does a simple thing like email create a server load ?

Scenario 1) It has reached its network limits - bandwidth ( this can be fixed by askig ISP to give me more bandwidth so ruled out) or TCP/IP ports - max 64000 per server is only allowed if I am not mistaken . I reckon this possibility is more relevant . What would be a solution then ? Add more network cards and enable bonding ? If yes will the bonding take care of load balancing ? Again only 1 IP so how can this counter this problem ? Maybe Virtual IP's ?

Scenario 2) It is not able to process requests - (Processor not enough ). Now the solution is probably Clustering . How do I go about implementing this? Who takes care of load balance ? Would it be like 4 servers each having webserver package running with a IP ?

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This is not a problem I have currently , but a likely scenario that I can come up with in Adminisrtation of large servers. –  Nishant Mar 7 '11 at 14:08
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up vote 3 down vote accepted

Considering your knowlege level you should find someone who knows what they're doing to evaluate your system and recommend upgrades or ways to improve efficiency.

Scenario 1a - Network bandwidth saturated. This is quite unlikely. You didn't mention anything about why you think there is a problem, but e-mail tends not to be bandwidth heavy unless you have a very large organization, and even then other factors of the system tend to be the bottleneck first.

Scenario 1b - Out of Ports. No, it doesn't work that way. Not even close.

Scenario 2 - Processor Capacity. This is more likely the issue, it also could be RAM, Disk Space, Disk Speed (throughput/latency), or something else entirely. Clustering is one potential option. A load balancing hardware device or specific software distributes connections; though you'll typically get more benefit from distributing the load intelligently by roll and/or destination.

Mail servers are not web servers, that's something else entirely. Computers must have IP addresses to work on the Internet; what kind of address will depend on your design.

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+1 for that opening comment; SF is not a substitute for years of IT experience. –  MadHatter Mar 7 '11 at 13:55
Thanks I am basically asking this to enhance my knowledge and also others who have less experience . Why does the TCP/IP 64000 ports not be a problem ? –  Nishant Mar 7 '11 at 14:07
TCP connections (which aren't the only type that use ports) keep track of connections based on Source IP, Source Port, Destination IP, and Destination Port. Assuming your server as 1 IP, 1 Port open, and unlimited capacity for processing connections: 600 Million PCs on the net * 63,000 Ports each (first 1k are reserved) * 1 (Your IP) * 1 (your Port) = ~38 Trillion possible connections. In case nobody has pointed it out yet, this site is For IT Professionals only, please see the FAQ for more details. –  Chris S Mar 7 '11 at 14:28
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