Resuming transfers to object storage

File transfer resume works differently when the target is object storage, and the process depends on the storage platform. Files are transferred to object storage in parts, which are finalized into a complete object once all parts uploaded.

Configuring file resume:

You can configure file resume as for regular transfers by using the GUI or command line. In the GUI, go to Connections > File Handling and select the options under the Resume section for When a complete file already exists at the destination and When checking files for differences drop-down menus. Files in object storage can be compared by using timestamps but not checksums.

To specify the same resume levels in an ascp command, use the options:
  • -k 0 – Always retransfer the entire file.
  • -k 1 – Compare file attributes and resume if they match, and retransfer if they do not.
  • -k 2 – Compare file attributes and the sparse file checksums; resume if they match, and retransfer if they do not.
  • -k 3 – Compare file attributes and the full file checksums; resume if they match, and retransfer if they do not.

Resume behavior:

  • Resume does not occur if the file is smaller than one part.
  • In general, a file resumes if at least one part was transferred to the destination.
  • During a transfer, browsing the storage through the GUI or Node API shows partial transfers as filename.partial files. These might be real files or placeholders, depending on the storage type. Real .partial files are visible with the storage's default browser whereas placeholder .partial files are not.
  • When the upload is complete, real .partial files are deleted and placeholder .partial files are no longer produced.