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Re: [Nbd] Performance tuning of nbd !?

Dirk von Suchodoletz wrote:

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?


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