Re: [Nbd] Performance tuning of nbd !?

[Paul Clements <paul.clements@...124...>]

Dirk von Suchodoletz wrote:

> When I try it over cable (okay, might be a little bit perverted - 25Mbit/s 
> ping of 15ms) or DSL (14Mbit/s ping of 35ms) the results drop to less than 
> 200kByte/sek. It is still possible to run a stateless client that way 
> (squashfs ontop of nbd), but you have to be patient while an app is 
> starting the first time.

> Is there any chance to get above the 10Mbit/s LAN rate in the WAN DSL or 
> cable scenarios!?

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:


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
net.ipv4.tcp_rmem = 4096 87380 1333000
net.ipv4.tcp_wmem = 4096 16384 1333000


The window size should be a little above your network "pipe size":

pipe = bandwidth * latency

--
Paul