Dirk von Suchodoletz wrote:
> Hi!
> 
>> Yes. I think you should be able to use about 70% of the bandwidth (I can get
>> about 32Mb/s out of 45Mb/s (T3) with 100ms latency). You might need to
>> increase your TCP window size and/or change the I/O scheduler you're using
>> for NBD. Switch to "deadline" scheduler if you're not using that one already.
>> And set the TCP window size, as follows:
> 
> Thanks for the tips - never changed something there before:) I set the
> scheduler to deadline ...
>  
>> In order to raise the window size to about 1 MB, the following sysctl
>> settings should be changed:
>>
>> net.core.rmem_max = 500000
>> net.core.wmem_max = 500000
> 
> ... increase TCP max buffer size (given in Byte?)
> 
>> net.ipv4.tcp_rmem = 4096 87380 1333000
>> net.ipv4.tcp_wmem = 4096 16384 1333000
> 
> What does all these values mean exactly?

It's minimum, default, and max memory size for send and receive windows.

They're documented in the kernel docs in 
/usr/src/linux/Documentation/networking/ip-sysctl.tct

>> The window size should be a little above your network "pipe size":
>>
>> pipe = bandwidth * latency
> 
> Changed the values to the examples given ... but no change. Sticking to 
> 130kB/s
> at the moment.

Sorry to hear that. I don't know of any other settings. These are the 
only ones I normally need to do. Can you achieve higher throughput with 
some other tool or protocol (scp, ftp, etc.)? Is there packet loss 
occurring?

--
Paul


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