The sentence is:
Hardware specifications rapidly become obsolete, but for the sake of illustration, a typical choice of machine for running an HDFS datanode and a YARN node manager in 2014 would have had the following specifications: somespec
So it looks like Third Conditional, which, in turn, is used when "both the condition and result are impossible now.", but it doesn't looks impossible to me. How meaning would had changed if it had have been just "would have"?
It is in fact the third conditional. The confusion lies in having two different uses of the verb have. First, have (and would) are auxiliary verbs used to denote the conditional mood. Second, have is also a verb in its own right meaning "possess." So you have the verb have in the past (third) conditional.
Have a look at these:
The machine has the following specifications.
The machine would have the following specifications.
Here we are using the verb have in its "ordinary" sense. The first sentence is present tense, the second is present (second) conditional.
Now, look at these:
The machine had the following specifications.
The machine would have had the following specifications.
The first sentence is past tense, again using the verb have in its "ordinary" sense. The second is past (third) conditional. The have in the second sentence is an auxiliary verb which is used with would in the past conditional. But the word had in the second sentence is again a use of the verb "have" in its "ordinary" sense. The "ordinary" sense of the verb has nothing to do with the structure of the conditional. The fact that it is the same verb is coincidental.
To further clarify this, have a look at these analogous sentences, with the verb feature substituted for the verb have:
The machine featured the following specifications.
The machine would have featured the following specifications.
You can see that the word have in the last sentence is again an auxiliary verb used as part of setting up the past conditional tense.
