Enable multi-session transfers

Enable multi-session transfers

1. In the navigation bar, go to Settings > Transfers.
2. Enable Multi-session by selecting the checkbox. If you want to disable this option, clear the checkbox.

Configure multi-session transfers

By default, multi-session transfers are split into 3 parallel transfer sessions with files being evenly distributed between the sessions regardless of file size. However, multi-session transfers can be configured to split files above a certain file size threshold between the sessions.

For example, when using the default file size threshold (100 MB), if the source directory contains multiple files, all files less than 100 MB are evenly distributed between sessions. However, files that are 100 MB or larger are first split and then distributed between sessions.

To adjust the multi-session transfer settings, follow these steps:

1. In the navigation bar, go to Settings > Transfers.
2. Change Number of sessions to adjust the number of transfer sessions used.
3. Enable the Split larger files into multiple sessions by selecting the checkbox, and specify the file size threshold.
   Note: While it's possible to increase the number of sessions used in multi-session transfers, the practical limitation is determined by the number of CPU cores on your computer.

Guidelines

Enabling multi-session transfers might not always result in faster transfers. For best results, enable multi-session if any of the following cases applies:

1. You have a very fast network connection (> 1 Gbps).
2. The server has a slower network connection than your network connection. For example, using cloud virtual machines.
3. You are transferring to or from a cluster of servers that have additional servers to handle increased traffic.

Limitation

There are several limitations when using multi-session transfers:

1. If encryption-at-rest (EAR) is used, then file size splitting is disabled.
2. If file size splitting is enabled, multi-session transfers are unable to be resumed. If the transfer is paused and started again, all files are retransferred.
3. HTTP fallback is disabled with multi-session transfers.

Troubleshooting

• Only a single transfer session started
  • Despite enabling multi-session in Aspera for desktop, the server might explicitly disable multi-session.
  • Check the transfer spec:
    • In the navigation bar, click Transfer activity.
    • Click the three-dot icon on the transfer that you want to troubleshoot, then click Info.
    • Go to the Transfer specification text area.
    • Find the field multi_session. If set to zero, the server has disabled multi-session transfers.
    • Find the field multi_session_threshold. If set and it is greater than zero, this value is used for the number of sessions. If zero, file size splitting is disabled.