Connecting a USB drive to a Synology NAS does not establish which device should supply the files. Before creating a USB Copy task, state the intended direction in plain language: copy this NAS folder to this USB folder, or import this USB folder into the NAS.

Use disposable sample data for the first rehearsal and keep the real source unchanged. Choose the task type that matches the direction, then read the displayed source and destination paths back against the written plan. A familiar drive label is not enough when several partitions or similarly named folders are present.

Choose the behaviour, not just the name

Synology describes Multi-versioned mode as producing a newly dated full-copy folder for each run. Mirroring makes the destination reflect the source's changes. Incremental mode copies new and changed source files, with additional conflict and organisation choices. Select the behaviour that serves the recovery requirement, including what should happen after a source file is deleted.

In an incremental task, inspect the Rename or Overwrite conflict choice and leave Delete source files after copy completes unselected unless moving and removing originals is explicitly intended. Also review any setting that flattens the source folder structure. Two documents with identical names in different subfolders need a deliberate destination arrangement.

Rehearse the next run as well

Create a small test containing nested folders and a file that will be edited between runs. Run the task manually, inspect the log and open the destination files. Then change the sample and run it again. Compare how the selected mode handles the older destination content; the first successful copy alone cannot demonstrate that behaviour.

Review file filters before trusting the item count, and keep automatic execution on insertion disabled during the rehearsal. Once the result matches the written plan, decide separately whether a plug-in trigger or schedule is appropriate. Label the drive and retain another recovery copy until the actual transfer has been checked.

Sources: Synology documentation 1.