You are absolutely correct. "How do you do" is an old fashioned introduction and is an obsolete synonym of "hello", and consequently the proper response is "how do you do?".
Mr Darlington: How do you do, Mrs Windermere?
Mrs Windermere: How do you do, Mr Darlington?
This exchange is exactly equivalent to the more modern (and at the time, more vulgar):
Mr Darlington: Hello, Mrs Windermere.
Mrs Windermere: Hello, Mr Darlington.
Note that the phrase "how do you do" has long since gone out of fashion in British English, and was never in fashion in American English.
Generally speaking, native speakers in both British English and American English now use the phrase hello instead, although how do you do does still persist in some formal settings in British English, generally during formal introductions, and lives on as howdy in some dialects of American English (and like how do you do, the correct response to howdy is howdy).
Don't be surprised if using this phrase that you receive odd looks - the phrase is excessively polite, and may easily be mistaken (even by native speakers) for the more common introduction "How are you?", to which the proper response is "I am fine, thank you, and you?".
"Workload" is a mass noun. Therefore, you would say, "Almost all of the workload is done on the server." If you wanted to use a count noun, you could say, "Almost all work is done by the server."
However, the phrase fragment "Almost all" is colloquial. For formal speech and writing, try "A majority of the work is done by the server." Further, "is done" is also colloquial. Try, "A majority of the work is performed by the server." In rough numbers "a majority" is anything from 50.1% to 99.9% There is no implied size beyond being the major portion of something. "Almost all" is perhaps less vague, but in professional writing, it sounds like you're avoiding the numbers.
In the first paragraph, I changed "on" to "by." When speaking of computer processing, there are regional uses of "on." Using "by" is less regional and more widely accepted. "I worked on my car" would imply that I repaired my car. If I said, "work was done on my car," I would also be implying "repair." If I said, "my car did all the work," I'm implying that the car's operation is a "work" of some kind. I could rephrase this to "all the work was done by my car." This latter example is similar to the usage in computer operations.
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