To copy files from a Synology NAS to an external hard drive, connect a compatible USB drive, open USB Copy in DSM, create a Data Export task, choose the folders and copy mode, then run the task. Check the task log and eject the drive in DSM before unplugging it. The exact options depend on your NAS model and DSM version.
Before you start: check the drive and NAS
USB Copy can export data to external USB or SD storage that the NAS recognizes. Synology lists FAT32, NTFS, ext3, ext4 and exFAT as examples; DSM external-device documentation also lists Btrfs and HFS Plus, with model-specific restrictions. Some NAS models support HFS Plus only for reading, and Btrfs is unavailable on a small number of models. Check the specifications for your exact NAS rather than assuming every format works. Synology USB Copy help · Synology External Devices help
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For exFAT, Synology’s article, last updated November 4, 2025, says DSM 7.3 and later includes support by default. DSM 7.0 through 7.2.2 requires installing exFAT Access. DSM 6.2.4 and earlier has separate package, model-support and licensing conditions, so verify the instructions for your release. Synology exFAT compatibility guidance
If DSM does not recognize the drive, formatting it for a supported file system may be necessary, but formatting erases the drive’s existing contents. Do not format until any files on it are backed up elsewhere. Choose a format based on NAS support and whether the computers that will use the drive can read it; there is no single best format for every setup.
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Copy files with USB Copy
- Connect the external hard drive to a USB port on the NAS. In DSM, the connected device appears as a shared folder named
usbshare[number]. - Open USB Copy in DSM and create a task. Select Data Export.
- Select the NAS source folder or folders and the destination folder on the external drive.
- Choose a copy mode based on what you want to keep on the drive.
- Set the file-conflict behavior, such as renaming or overwriting files, and configure filename or extension filters if needed.
- Apply the task and start it in USB Copy. Depending on the task configuration and NAS hardware, it may also run on a schedule, when the drive is inserted, or using a supported hardware Copy button.
- Check the task status and logs for errors or warnings. When the copy is finished, use DSM’s eject option before physically disconnecting the drive.
DSM’s exact interface, USB Copy availability and hardware-button support can vary by model and software version. The Copy button is supported only on some models and may offer fewer options than running a configured task through USB Copy. Synology USB Copy help
Choose the copy mode that fits your goal
| Mode | What it does | Choose it when |
|---|---|---|
| Multi-versioned | Creates a full copy in a folder named for the run time each time the task runs. Rotation can remove older versions if enabled. | You want separate dated copies and have enough destination space for them. |
| Mirroring | Copies source changes so the destination folder reflects the source. | You want the external folder to track the current source state rather than keep separate full runs. |
| Incremental | Copies newly added and modified source files. | You want repeated runs to add new or changed files without making a fresh full copy each time. |
Mirroring is not the same as keeping historical backups: its purpose is to make the destination reflect source changes. Review the mode description in USB Copy before running a task, especially when the drive already contains files you intend to keep. Synology USB Copy help
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Resolve common copy problems
The NAS does not recognize the drive
Confirm that the drive’s file system is supported by your specific NAS and DSM release. If formatting is required, first copy any existing contents elsewhere because formatting erases them. DSM shows recognized external storage as a usbshare[number] shared folder. Synology External Devices help
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Check your DSM version and follow Synology’s version-specific exFAT guidance: DSM 7.3 and later includes support by default, while DSM 7.0–7.2.2 requires exFAT Access. Earlier DSM versions have different requirements. Synology exFAT compatibility guidance
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Some files are missing or skipped
Review the USB Copy filters and task log. Synology documents restrictions on names, including names beginning with ._ or .SYNOPPSDB, as well as certain reserved names. Filters may also intentionally exclude matching filenames or extensions. Synology USB Copy help
Renamed files collide
FAT32 and exFAT do not allow some characters that may appear in source filenames. Synology warns that automatic replacement of invalid characters can make distinct names collide. Check the conflict policy and task log; if necessary, consider a different file system that is supported by both the NAS and the computers that need to access the drive. Synology USB Copy help
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Unexpected files beginning with ._ appear
macOS can create auxiliary files that store extended-attribute data. Synology explains that copying to file systems other than ext4 or Btrfs can produce accompanying dot-underscore files. Their presence does not by itself mean the main file failed to copy. Synology explanation of dot-underscore files
When Hyper Backup is a better fit
USB Copy makes an ordinary folder export. If you want a backup workflow to a USB destination, Synology’s Hyper Backup guide covers DSM 6.0 and later. Its single-version option stores files in their original formats and folder structure so they can be viewed directly on other devices. Multi-version Hyper Backup saves data in .hbk files and supports features such as encryption and compression; do not expect that destination to look like a normal set of copied folders. Synology Hyper Backup USB guide
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