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i am doing sizing for a new infrastructure.. and I need to load balance a set of servers to gain performance.
But I'm thinking, would it help even more if I run xen and do virtualization on each box.
For example, if I originally wanted to load-balance 4 boxes.. and say I set virtualization up such that each box have 2 guest domains doing the webserver part.. essentially i have 8 logical boxes yeah?
Virtualization won't provide performance increase but will utilize and downsize the amount of hardware you'll need to cut costs. Depending on what the server will be doing, usually virtualizing them is the way to go nowadays.
Here's why: "virtualization does not multiply the CPU resource; it can only divide it."
Virtualization can allow that single piece of silicon inside that single machine to very-deftly wear either one of two hats, but it cannot cause one piece of silicon to magically acquire twice the "load-bearing capacity" that it used to have.
When to put to a genuine computational test (which rarely actually happens...) a virtual processor by-definition will have somewhat less than 50% of the capacity of a real one. For "load balancing" purposes, this is all that matters.
yah but the idea of using virtualization is to harness unused cpu power isn't it?
cause there's only so much one instance of the OS can use at one time...
so i am thinking with virtualization, i can use the same piece of silicon in a more efficient manner, and with a load-balancer thrown in to the picture... won't it somewhat increase performance overall?
If your going to load balance two identical servers that are virtualized, you'll only get performance increases say if they were on different hardware.
Say ServerA and ServerB are identical. You need to have 4 virtual servers on each, between those there are actually only 4 servers as you want to load balance them. Put the first 4 on ServerA and the other 4 on ServerB. Depending on how you load balance, that would be the only way to get any performance out of them unless one of them is just for failover, etc.
But virtualising servers is the way to go if they aren't too intensive and just need to be standalone. On average from what I've read, an average server will only uses 15% utilization overall, hence the reasoning for virtualising, it's a good way to not have a server waste resources that could go to other things, like other servers and OS's on the same box, etc.
yah i am thinking along that line but just that say
ServerA and ServerB, each have 2 virtual servers.
So that makes a total of 4 logical servers over 2 physical boxes yah
There are 2 services of intent here.. so say its Service1 and Service2
So therefore.. ServerA.1 (refering to 1st virtual instance of ServerA) has service1, ServerA.2 has Service2
ServerB.1 has Service1, ServerB.2 has Service2
and i do load balancing this way.
Will I be getting a better value for my buck this way?
And say for the 4 virtual instances.. they are used for Service1 only, and i load-balance them..
will I be getting better performance since technically, I am squeezing more potential out of per-box