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To copy files from a Synology NAS to an external hard drive, connect the drive to the NAS and use Synology’s USB Copy package to create a Data Export task. Select the source folders, choose a copy mode, and run the task. Check the task log, then eject the drive in DSM before unplugging it.
Before you start: check drive and NAS compatibility
USB Copy can use external USB or SD storage that the NAS recognizes. Supported file systems depend on the NAS model and DSM version. Synology documentation lists FAT32, NTFS, ext3, ext4, and exFAT as examples; DSM’s external-device help also lists Btrfs and HFS Plus, with model-specific limitations. Some models support HFS Plus only for reading, and Btrfs is unavailable on a small number of models. Check the specifications and DSM help for your exact NAS before relying on a format. Synology USB Copy help and DSM External Devices help describe supported formats and limitations.
Check exFAT against your DSM version
Synology says exFAT support is included by default in DSM 7.3 and later. DSM 7.0 through 7.2.2 requires the exFAT Access package. DSM 6.2.4 and earlier has different licensing and model-support conditions, so check Synology’s version-specific guidance rather than assuming an exFAT drive will work. This information is from Synology’s article last updated November 4, 2025: Can I use exFAT external storage devices with my Synology NAS?
If DSM does not recognize the drive, it may need a file system supported by your model. Formatting erases the drive’s existing contents, so copy anything important elsewhere before formatting. Choose a format based on both NAS support and the computers that must read the drive afterward; there is no one format that is right for every setup.
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Copy NAS files with USB Copy
- Connect the external hard drive to a USB port on the NAS. In DSM, confirm that the drive appears as external storage. DSM presents connected USB storage as a shared folder named
usbshare[number]. - Open USB Copy in DSM. If it is not available, check package availability for your NAS model and DSM version.
- Create a task and select Data Export.
- Choose the NAS source folder or folders and the destination folder on the external drive.
- Select a copy mode. Choose the conflict behavior, such as renaming or overwriting files, and set any filename or extension filters you need.
- Apply the task and start it in USB Copy. Depending on the task settings and NAS hardware, you can also configure a schedule or run a task when a drive is inserted. A physical Copy button is available only on supported models and may have narrower behavior than a task started in DSM.
- Check the task status and log for errors or warnings. When the copy is finished, use DSM’s eject option for the external drive before disconnecting it.
Exact interface labels and hardware features can vary by DSM release and NAS model. Synology’s USB Copy instructions cover task setup, execution, filters, and logs; External Devices help explains drive recognition and ejection.
Choose the copy mode that fits your goal
| Mode | What happens | Best fit |
|---|---|---|
| Multi-versioned | Each run makes a full copy in a folder named for the run time. Rotation can remove older versions if enabled. | Keep separate dated copies, provided the drive has enough space for them. |
| Mirroring | The destination is made to reflect source changes, resulting in a mirror of the source folder. | Keep the destination aligned with the current source state. Do not choose it if you need older file states retained. |
| Incremental | Copies newly added and modified source files. | Run repeat copies without making a fresh full copy each time. |
These are the documented behaviors in Synology’s USB Copy help. Consider the destination’s available capacity, especially for multi-versioned copies.
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When files are missing or renamed
Some files were skipped
Review the USB Copy task filters and log. Synology’s help says names should not start with ._ or .SYNOPPSDB and also lists reserved names that USB Copy excludes. A filter can also exclude files by name or extension, so check the task configuration if expected files are absent. USB Copy help
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FAT32 and exFAT cannot represent some characters used in filenames. Synology warns that automatic renaming of such names can make distinct source filenames collide on the destination. Review the conflict setting and logs; if the problem persists, consider another file system only if it is supported by your NAS and compatible with the devices that need to read the drive. USB Copy help
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Unexpected files beginning with ._
macOS can create auxiliary files containing extended-attribute data. Synology explains that copying to external file systems other than ext4 or Btrfs can produce accompanying dot-underscore files. Their presence does not necessarily mean the main file failed to copy. Why are files beginning with ._ created when I copy or back up files to an external storage device?
Use Hyper Backup when you want a backup set
USB Copy creates exported files on the external drive. If you want a backup workflow instead, Hyper Backup supports USB destinations. Its single-version option keeps files in their original formats and folder structure so they can be viewed directly on other devices. Multi-version Hyper Backup data is stored as .hbk files and supports features such as encryption and compression; it is not an ordinary folder copy that you can browse in the same way. Synology’s guide covers DSM 6.0 and later: How do I back up my data to a local shared folder or USB using Hyper Backup?
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