Does IP Aliasing decrease performance?

I was reading a whitepaper on Web / App server configurations. It stated that the example setup used multiple ports attached to a single IP address, and that this had better performance then IP Aliasing.

Is this true?

My servers are behind a Cisco CSS load balancer, so I could use either IP Aliasing or a single IP address with various web server process on different ports. The server in question has 12 JVM web server processes running.

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giltjrConnect With a Mentor Commented:
Umm, well really no.  Twelve IP addresses with a single port each is no more or less overhead that one IP address with twelve unique ports.   It is still 12 ports that the box must listen on.

I would question running 12 JVM's for only 700 concurrent connections, or is that 700 concurrent connection per JVM instance?   CPU usages is low, how is memory usage?  Of couse I don't know the application, if it is single threaded, I guess you need 12 JVM's to process 12 requestes.

I would stick with the 12 unique IP addresses, that way if needed you could take some of the JVM's and move to a second box and move their IP addresses with them and there are no application related changes.  You just go from 1 box with 12 addresses and 12 JVM's to two boxes with 6 IP addresses and 6 JVM's.
What You mean by IP Aliasing?
Surely IP based virtualHosts will act better/faster than NameBasedVirtualHosts - but the impact is negligible.
If You mean that one eth card has binded more that one IP - I belive there is no performance loose at all(confronting to one ip any many ports).
p1800volvoAuthor Commented:
The URL resolves to a CSS. It then sends traffic via round robin to 12 IP addresses. The server has an interface that accepts connections from those 12 IP Addresses. This helps with web server stability by sending traffic to individual JVM Web Server processes. I did not implement the system, just inherited it.

Is this hurting performance vs. a single IP address and using ports that the JVM's would listen in on?

This box accepts up to 700 concurrent connections for an app server behind it.

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So You saying he server has eth card with binded 12 ip addresses?
> Is this hurting performance vs. a single IP address and using ports that the JVM's would listen in on?
Depends - if the web server is binded to individual IPs - Yes, linux have to browse list of 12 addresses instead of one.
If the server is bind to ANY( address - the browsing is not needed, therefore performance should not decrease.
To verify that: netstat -ltnp
So you have 12 JVM processes running each with their own IP address?

What type of box is this running on?

I would say that if you are running 12 JVM's  the least of your overhead problems deal with Linux have mutiple IP addresses to listen on.
p1800volvoAuthor Commented:
Currently, it's a Sun 280, 2 way box with 8 Gigs of RAM, running Solaris 8. CPU is use is low since it is only serving pages given to it by a big 880 box.

We are going to Linux and wanted to set it up for best performance. From what I am reading, that would seem to be to configure the new box using a single IP addy on a single card with the 12 JVM listening to 12 different port numbers.
I thought I give better explanation of when & why it can be performance loose. Whatever...
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