Fieldwork data handoff: plan a USB transfer

Fieldwork data can take longer to hand off than expected, especially when a drive is slow or a folder contains thousands of small files. A transfer that runs late can delay a team, a lab, or the next stage of analysis.

Before you copy the final dataset, check the storage device's real speed and plan time for copying and verification. The USB & SD Speed Test measures flash drive and memory card read and write speed. It can help you spot a slow destination, but it does not confirm that your research files copied correctly.

Plan and test the handoff

1. Open the USB & SD Speed Test on the computer and with the drive or card reader you plan to use. Follow the tool's instructions to check the storage device. Use a drive that is empty or backed up, and follow any instructions the test gives about its data.
2. Write down the test's read and write speeds. For a handoff, write speed is usually the more useful figure because it affects how quickly files can be copied onto the drive.
3. Estimate the transfer time from the total data size and the measured write speed. As a rough example, 10 GB at 20 MB/s takes about 8 minutes and 20 seconds in ideal conditions. Allow extra time for file-system overhead, small files, and verification.
4. Before copying, organize the data into clearly named folders and check the destination has enough free space. Copy a representative sample first, then open several files from the destination to make sure they are readable.
5. Copy the complete dataset, compare the source and destination folder contents, and keep the original data until the recipient confirms they received and opened the handoff.

For the fairest speed estimate, test the actual drive, reader, port, and computer you will use. A different USB port or card reader can change the result. A benchmark also cannot predict every transfer: copying many small files can take longer than copying one large file of the same total size.

What the speed results mean

Write speed is much lower than expected

The drive may take longer to receive the data than your estimate suggests. Check that you are looking at write speed, not read speed, and use the slower measured rate when planning. The speed test measures transfer performance, not whether the storage is genuine, healthy, or suitable for long-term archiving.

Read speed is much higher than write speed

This is common. A drive can deliver files quickly to a computer but accept new files more slowly. Base the handoff schedule on write speed. If the recipient needs to work from the drive, read speed matters too, but it does not reduce the time needed to copy data onto it.

The result changes between runs

Other activity can affect a measurement. A drive may also slow during a long write, and a card reader or adapter can limit performance. Close unnecessary file transfers and repeat the test under the same conditions. Treat a single result as a planning estimate, not a guaranteed transfer rate.

The speed looks fine, but the file copy is slow

The benchmark may use a different pattern of data than your handoff. Large files often copy differently from folders with many small items. The source drive, computer, encryption, file system, or a busy background task can also slow the real copy. Test a sample of the actual dataset to get a more realistic estimate.

Fix a slow or unreliable handoff

1. Protect the only copy first. Keep the source data untouched and make a separate backup before testing or copying. Do not use a drive containing the only copy of important fieldwork data as a test destination.
2. Connect the drive directly. Try another USB port on the computer and avoid an unpowered hub or a chain of adapters. For an SD card, reseat it and check whether the card reader, rather than the card, is limiting the transfer.
3. Pause other transfers. Stop large downloads, backups, and copies to or from the same storage device. Close applications that are actively reading the source data, then test again.
4. Check the available space and file system. Make sure the destination has room for the full dataset and any extra files created during the handoff. If you need to reformat a drive for compatibility, back it up first: formatting erases its contents.
5. Copy in manageable groups. If a huge folder fails or stalls, copy it in smaller batches and note which batch causes trouble. Keep the source intact while you investigate, rather than deleting files as they copy.
6. Eject the drive before unplugging it. On Windows 11, use File Explorer › This PC, right-click the drive, and choose Eject. On macOS, use the drive's eject icon in Finder or select it and choose File › Eject. Wait until the drive disappears before disconnecting it.

Verify the data, not just the drive

A speed test tells you how quickly the storage device moves test data. It does not prove that a particular copy is complete or unchanged. After copying, compare the number of files and folders in the source and destination, check the total size where available, and open a few files from different folders. Include files from the start and end of a long recording or collection, not just the first item.

If the data is valuable or difficult to collect again, make two copies on separate storage devices and keep the original until the recipient confirms the handoff. Label the drive with the project name and collection date, but avoid putting sensitive participant details on the outside. Store the drive in a protective case, and agree with the recipient on a secure way to return or retain it.

Keep a short handoff note with the folder names, approximate data size, copy date, and any files that still need review.