On March 31, 2011 9:36 , Janne H <jannehson51@xxxxxxxxx> wrote:
What does 'much "closer"' mean?The server is in Amazon EC2 cloud, and ipA is another EC2 instance. ipB is from the office, and ab reports a noticeble difference in latency, about 43 ms when accessing from ipB.
Does "ping" report the same round-trip time when you ping your web server from ipA as compared to when you ping your web server from ipB? If the answer is "no", then this isn't a problem with Apache.
Also, what does traceroute show beween ipA and your web server, as compared to between ipB and your web server? Again, if it takes longer to do a traceroute from ipB, the problem is not with Apache. And traceroute can help you find any significant differences in network topology between the two network paths.
There is almost zero load on the machines. The EC2 machines are small instances (1 core each) and the office machine a common PC with two cores. They are all running Ubuntu Linux (LTS 10.04 in EC2) and 10.10 in office PC. I'm not sure how to answer about the kernel and networking stacks.
Basically, are there any differences between how the two machines are configured?
Since these are Amazon EC2 instances: are you absolutely positive that Amazon is hosting both of them on physically identical hardware? If ipB is on much older / slower physical hardware, that may account for the difference you are seeing. Also, do you have any way of knowing what instances from other customers are sharing the same hardware as you? For example, if there are more instances sharing the hardware that ipB is hosted on, or if the instances for other customers on the hardware for ipB are putting the hardware over heavier CPU or IO load, then that also could account for the difference you are seeing.
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