Why external drives slow down through USB hubs
Learn why an external drive slows down through some USB hubs, how to compare its speed, and which cable, port, or power fix to try.
Your external drive copies files quickly when plugged into your computer, but crawls through a USB hub. The hub may be limiting the connection, sharing its bandwidth with other devices, or struggling to supply enough power. A USB-C plug alone does not guarantee a fast connection.
Compare the same drive through the hub and directly into the computer. If it is a USB flash drive or memory card, the USB & SD Speed Test can also help you check its read and write speed.
Compare the drive through the hub and directly
- For a USB flash drive or memory card, open the USB & SD Speed Test and test the device. For an external hard drive or SSD, use a large file you already have and time how long the same copy takes.
- Connect the drive to the hub as you normally do. Wait for any current file transfer to finish, then run the test or copy the file. Note the result.
- Disconnect other devices from the hub, especially other storage devices, webcams, and devices transferring data. Repeat the test or copy.
- Connect the drive directly to a computer USB port using the same cable, if possible. Run the same test or copy the same file again.
- Repeat each comparison once or twice. Use a large file for file-copy tests, since small files can make even a fast drive appear slow.
Keep the drive, file, and computer the same between tests. Do not compare a nearly full drive with an empty one, or a transfer that is still running with one that has finished.
What the result means
The drive is much faster when connected directly
The hub, its cable, its power supply, or the connection to the computer is likely the bottleneck. If removing other devices improves the result, the hub's shared connection is probably busy. Try the fixes below.
The drive is slow through both connections
The hub may not be the cause. The drive itself, its cable, the file system, or the computer's USB port may be limiting speed. Check the drive with a different cable or computer before replacing the hub.
Speed drops only when other devices are connected
Devices on a hub share its connection back to the computer. A second storage device transferring files can take part of that capacity, and some hubs put multiple ports on the same internal connection. Move one busy device to another port on the computer, or use a separate hub for it.
The drive disconnects or pauses instead of staying slow
This can point to insufficient power, a loose cable, or an unstable hub. A bus-powered hub draws power from the computer. Some external hard drives need more power than that setup can reliably provide, especially when they start up or work hard.
How to fix it
- Try another port on the hub. Some hubs have a mix of faster and slower ports, or ports that share an internal connection differently. Check the labels or manual rather than relying on the shape or color of a port.
- Disconnect other busy devices. Retest with only the drive attached. If speed returns, keep high-bandwidth devices on separate computer ports where possible.
- Check the hub and cable ratings. A connection is limited by its slowest part: the computer port, hub, hub cable, drive cable, or drive. A USB 2.0 link has a theoretical limit of 480 megabits per second, and real transfers are lower. A USB-C connector describes the plug shape, not the speed it supports.
- Use the drive's original cable or a known data cable. Some cables are made mainly for charging, and some support only older USB speeds. Swap one cable at a time so you can tell whether it changes the result.
- Connect a power adapter to the hub. If the hub has a power input, use its correct adapter. For a hard drive that still disconnects, connect it directly to the computer or use a hub designed to provide enough power.
- Try a different computer port or hub. A port on the computer itself avoids the hub's extra connection. If another hub gives the drive its normal speed, replace the slow or unreliable hub.
- Check for limits in the drive itself. Some drives slow down during long writes as their fast cache fills, or when they get hot. If speed starts high and then falls even when connected directly, let the drive cool and repeat a longer transfer.
Why two hubs with the same plugs can behave differently
A hub is not just a set of extra sockets. It connects those sockets to the computer through one upstream link, and devices on it may share that link. If the hub or its cable supports only USB 2.0, a fast SSD cannot reach its usual speed through it, even if the drive and computer support a newer USB version.
Power and data speed are separate issues. A powered hub can provide more electrical power, but it cannot make an older, slower data link faster. Likewise, a fast hub will not fix a slow cable or a drive that has reached its own write limit.
If a drive is consistently slow only through one hub after you have checked its ports, cables, and power, use another hub or connect the drive directly. A faster-looking connector is not proof of a faster connection.
