# iperf maxed out at 936 Mbps (117 MB/s). Need help tuning it further.



## einthusan (Jun 3, 2012)

I have tried tuning the network card for several weeks and the most I was able to get was 117 MB/s (936 Mbps). The maximum should be 1000 Mbps (125 MB/s). Yes the difference is just 8 MB/s but thats a potential 20 TB over 1 month.

```
8 (MB/sec) * 3600 (sec/hr) * 24 (hr/day) * 30 (days/month) = 20,736,000 (MB/month) = 20 TB/month
```
Can anyone please help me tune the network card? The maximum reported by others thus far is 117 MB/s, is it even possible to reach 125 MB/s over 1 Gigabit NIC?


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## einthusan (Jun 3, 2012)

Actually, I found this thread where two people have claimed to hit 125 MB/s for some time.
http://forums.whirlpool.net.au/archive/1667275

Both of them are using Apple xServe. One of them even posted a graph.


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## Bobbla (Jun 4, 2012)

Chances are that you get some packet loss at those speeds are high. I personally reach about 109MB/s when transferring files between my workstation and server via a switch and 2.5m of cable. But I am not sure if it is the hard disks fault or not as I have not done any testing.

I'm curious thou*gh*, whats your packet loss rate?

BTW, more info is always a plus. NIC name, cable length and category as well as any switches the data is passes thr*o*u*gh*.

NB! I am no expert.


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## einthusan (Jun 4, 2012)

How can I check the packet loss? I am with a dedicated server provider so I am not sure about the details. However I am testing between servers in the same datacenter. It's an Intel NIC, not sure of the model but it's an "enterprise" level NIC and very good. I think it's an OS/NIC tuning issue more than a hardware problem.


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## t1066 (Jun 4, 2012)

netstat() is your friend.

`$ netstat -ih`

should show whether there are dropped packets.


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## SirDice (Jun 4, 2012)

1.000 Mbps = 1.000.000.000 bps = 125 MB/s = 119 MiB/s

http://en.wikipedia.org/wiki/Binary_prefix#Data_transmission_and_clock_rates

Subtract some overhead like source and destination MAC addresses, source and destination IP addresses, options, etc.

117 MiB/s is quite good. I wouldn't worry about it.


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## einthusan (Jun 7, 2012)

Thanks guys. netstat shows no packet drops either so that's good. There is so much misguiding information out there regarding 1 GbE max throughput. Thanks for clearing it up with the wiki page.


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