D Teed wrote:
Be careful comparing the data transfer rate. That
measure how fast you are writing the info to disk, and
in the end, that is the only thing that matters in
the performance of udpcast. Time the job with a clock/watch
and compare the times.
Indeed. The bandwidth displayed by udpcast is the bandwidth needed to
transmit the *compressed* data. If you have a very compressible disk,
the limiting factor now becomes the disk read speed, and compressed
(network) bandwidth will drop. However, the useful bandwidth
(uncompressed data), which is not displayed, will rise.
At our institution, using gzip, we write 40GB to P4-M
in 34 minutes, regardless how much non-zeroed data there is to write
Normally, if everything works correctly, it should be quicker to
transmit images which contain lots of zeroed data. However, in such
case, the *displayed* bandwidth (network bandwidth) will be lower,
because such data still needs to be read from the disk, and udp-sender
will end up waiting for the disk, rather than the network.