What does this error mean

I ran a sample restore job and after restoring everything (I think correctly) I got this error:

failed to patch file: “xxxxxxx.pst” with data from local file

What does “patch” exactly mean?

Was it really an error (meaning the restore failed) or was it just a warning (meaning there was an problem but Duplicati worked around it)?

When doing a restore Duplicati tries to use blocks from local files that haven’t changed since the last backup rather than going through the expense of downloading, decrypting, and unzipping the blocks from the remote destination.

My guess is that the error you got was caused by Duplicati trying to access your Outlook PST file while outlook was running (so the file was in use) but WITHOUT a VSS / Shadow Copy --snapshot-policy setting. (I suspect - but have not checked - that the restore process may not actually use the --snapshot-policy in which case this is a bug / failure point that should be addressed.)

I would suggest trying the restore again but with one or both of this in place:

  • Outlook not running (so the local PST is no longer in use and can be accessed for local block use
  • set --no-local-blocks=true (to tell Duplicati not to try and use local blocks at all and ONLY use the remote destination blocks)

Duplicati will attempt to use data from source files to minimize the amount of downloaded data. Use this option to skip this optimization and only use remote data.
Default value: “false”