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bbcp is a point-to-point network file copy application developed at SLAC. It was initially used by the BaBar Collaboration to transfer massive amounts of data between numerious numerous sites of the Collaboration. The protocol has been specifically designed for WAN. In particular, it allows sending data in multiple simultaneous streams.
This document gives only some tips that are intended to help readers to begin using the tool to tranfer transfer LCLS data. To find the complete documentation on the tool please visit the official site: http://www.slac.stanford.edu/~abh/bbcp/.
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Since bbcp is a peer-to-peer application then no permenently permanently running server process is required - you just invoke the bbcp executabe executable on a source machine and in response another bbcp executable is started on the target machine. A more sophisticated scenario involves using the three-party scheme: the source and target machines do not need to be the same (third) machine that you initiate the file transfer from. Please, consult the official bbcp documentation for further detail on that subject. At the mean time, all examples presented in the current document will be based on a simple two-party mode.
You can either download a pre-buit build version of bbcp or build it yourself from source. See building instruction at (or clone the git repo: git clone http://www.slac.stanford.edu/~abh/bbcp/bbcp.git). For more information check the download section in the bbcp documentation.
Make sure the bbcp executable is available in the executable search path at both sides.
bbcp on psexport
bbcp is installed in /usr/bin/bbcp on the psexport machines.
Usage
First tests
The first test would be to transfer something on the same host. In the following example, you'll be transferring data from the special device (generating zeroes) into the null sink:
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% bbcp -P 2 localhost:/dev/zero /dev/null
user@localhost's password:
bbcp: Creating /dev/null/zero
bbcp: At 090413 17:37:56 copy 0% complete; 811858.2 KB/s
bbcp: At 090413 17:37:58 copy 0% complete; 819277.7 KB/s
bbcp: At 090413 17:38:00 copy 0% complete; 827783.2 KB/s
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By default bbcp will use 4 simultaneous streams to send data over the network. You can increase (or decrease) that number by using the "-s" opting and specified the desired number of streams:
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% bbcp -P 2 -s 32 localhost:/dev/zero /dev/null
user@localhost's password:
bbcp: Creating /dev/null/zero
bbcp: At 090413 18:12:04 copy 0% complete; 113401.7 KB/s
bbcp: At 090413 18:12:06 copy 0% complete; 113695.8 KB/s
bbcp: At 090413 18:12:08 copy 0% complete; 113981.2 KB/s
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% bbcp -P 2 -s 1 localhost:/dev/zero /dev/null
user@localhost's password:
bbcp: Creating /dev/null/zero
bbcp: At 090413 18:13:10 copy 0% complete; 99670.7 KB/s
bbcp: At 090413 18:13:12 copy 0% complete; 100668.6 KB/s
bbcp: At 090413 18:13:14 copy 0% complete; 101580.4 KB/s
bbcp: At 090413 18:13:16 copy 0% complete; 101393.9 KB/s
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Another parameter worth to consider is so called TCP window size. By default bbcp would set it to 64 KBytes. The corresponding option for bbcp is called "-w". In the following example, the desired window size is set to 2 MBytes:
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% bbcp -P 2 -w 2M localhost:/dev/zero /dev/null
user@localhost's password:
bbcp: Creating /dev/null/zero
bbcp: At 090413 18:12:04 copy 0% complete; 113401.7 KB/s
bbcp: At 090413 18:12:06 copy 0% complete; 113695.8 KB/s
bbcp: At 090413 18:12:08 copy 0% complete; 113981.2 KB/s
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Please use the data mover pool to transfer data to your home institution:
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psexport.slac.stanford.edu
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The following example will copy the source file <srcfilename> from the LCLS mover node psimport psexport to the destination file <dstfilename> on the local machine, printing the progress every 15 seconds, using 32 streams and a windows size of 2MB:
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% bbcp -P 15 -s 32 -w 2M psexport.slac.stanford.edu:<srcfilename> <dstfilename>
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If the bbcp executable isn't available in the executable search path of user 'user' at remote host 'SomeRemoteHost' then this will be reported as follows:
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% bbcp -P 2 user@SomeRemoteHost:/dev/zero /dev/null
bbcp: Command not found.
bbcp: Unable to allocate more than 0 of 4 data streams.
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Sometimes a firewall (either at SLAC or at a remote site) may block certain (ranges of) ports. Unfortunatelly, it's hard to diagnose this problem directly. bbcp would report this typically as follows:
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% bbcp -P 2 user@SomeRemoteHost:/dev/zero /dev/null
bbcp: Accept timed out on port 5031
bbcp: Unable to allocate more than 0 of 4 data streams.
Killed by signal 15.
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Note, that the actual port number may vary in each specific case because bbcp would attempt to dynamically allocate the next available (at the remote server machine) port. A workaround for this problem is to use option "-z" which would use reverse connection protocol (i.e., sink to source):
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% bbcp -z -P 2 user@SomeRemoteHost:/dev/zero /dev/null
user@SomeRemoteHost's password:
bbcp: Creating /dev/null/zero
bbcp: At 090414 02:59:48 copy 0% complete; 5461.3 KB/s
bbcp: At 090414 02:59:50 copy 0% complete; 13639.7 KB/s
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TCP Tuneup
One cane can find useful tips on how to tun up TCP parameters on machines involved into the data transfer to get the highest data transfer rate with bbcp:
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