Data Transfer Nodes
Overview
The data transfer nodes are NERSC servers dedicated to performing transfers between NERSC data storage resources such as HPSS and the NERSC Global Filesystem (NGF), and storage resources at other sites including the Leadership Computing Facility at ORNL (Oak Ridge National Laboratory). These nodes are being managed (and monitored for performance) as part of a collaborative effort between ESnet, NERSC, and ORNL to enable high performance data movement over the high-bandwidth 10Gb ESnet wide-area network (WAN).
Restrictions
In order to keep the data transfer nodes performing optimally for data transfers, we request that users restrict interactive use of these systems to tasks that are related to preparing data for transfer or are directly related to data transfer of some form or fashion. Examples of intended usage would be running python scripts to download data from a remote source, running client software to load data from a file system into a remote database, or compressing (gzip) or bundling (tar) files in preparation for data transfer. Examples of that should not be done include running a database on the server to do data processing, or running tests that saturate the nodes resources. The goal in all this is to maintain data transfer systems that have adequate memory and CPU available for interactive user data transfers.
Configuration
There are two data transfer nodes deployed at NERSC:
- dtn01.nersc.gov
- dtn02.nersc.gov
Each node includes two dual-core AMD Opteron processors operating at 3.0 GHz, 8 GB of shared memory, two fibre-channel interfaces (4 GB/s each), and two Ethernet interfaces (10 Gb/s each). The nodes are running CentOS 5.2, a RedHat Enterprise Linux derivative. Third-party software is managed via modules. As with other NERSC systems, shell configuration files ("dot files") are under the control of NERSC; users should only modify ".ext" files.
Oak Ridge has deployed similar data transfer nodes named dtn01.ccs.ornl.gov and dtn02.ccs.ornl.gov. See Data Transfer Nodes at Oak Ridge.
Access
All NERSC users are automatically given access to the data transfer nodes. The nodes support both interactive use via SSH (direct login) or data transfer using GridFTP services.
Available File Systems
The NERSC data transfer nodes use global home, gloabl scratch and the project directory. See NERSC File Systems. Please note that /tmp is very small. Althought certain common tools (e.g., vi) use /tmp for temporary storage, users should never explicitly use /tmp for data.
File Transfer Software
For smaller files you can use Secure Copy (SCP) or Secure FTP (SFTP) to transfer files between two hosts. See Using SCP and SFTP at NERSC. For larger files BBCP and GridFTP provide better transfer rates; in addition, Globus Online makes GridFTP transfers trivial so users do not have to learn command line options for manual performance tuning. Globus Online also does automatic performance tuning and has been shown to perform comparable to -- or even better (in some cases) than -- expert-tuned GridFTP. See Using BBCP at NERSC and Grid Data Transfer.
Special commands can be used for data transfers to or from the HPSS mass storage system. See Storing and Retrieving HPSS Data.
