Roy M. wrote:
According to 3.0 manual:
=========
weighted-round-robin
to define a set of parents which should be used in a round-robin
fashion with the frequency of each parent being based on the round
trip time. Closer parents are used more often.
=========
Currently I have 3 Apache web servers, A, B, C,
where B has Dual CPU and more memory, they are under the same private network.
So I assign B with more weight.
#A
parent 80 0 no-query originserver weighted-round-robin login=PASS weight=1
#B
parent 80 0 no-query originserver weighted-round-robin login=PASS weight=2
#C
parent 80 0 no-query originserver weighted-round-robin login=PASS weight=1
However, from the access log from these 3 web servers, I found that
the MISS request to #B is only around 130% higher than A and C
Is it normal or I misunderstood the weighted-round-robin settings?
Small mis-reading perhapse. weighted-round-robin works the same as
round-robin only its based on the peer RTT (network delay to reach peer).
In vanilla robin, the counter gets 1 added, which evenly balances
requests through the peers, regardless of network trouble or anything else.
In weighted, the counter gets RTT/weight, which balances things more in
favour of close peers. But weight= can give an extra boost to preferred
peers or a manual balancing if the expected RTT (in ms) to that peer is
large. The division is never allowed to produce a non-integer or stat
under 1.
Amos
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