How to check for a drive bottleneck before resale

A computer can feel slow even when its processor and memory are fine. Before you sell it, check whether the storage drive is holding it back, or whether a cable, port, or background task is making the drive look slow.

The Storage Test measures large-file read and write speed, plus small writes, in your browser. The results can help you spot a pattern, but they do not certify drive health or prove the advertised model or capacity.

Test the drive consistently

1. Open the Storage Test on the computer you plan to sell. If you are checking an external drive, connect it before you start.
2. Close file copies, downloads, backups, game launchers, and other tasks that might use the drive. Wait until activity settles.
3. Run the test and note the large-file read speed, large-file write speed, and small-write result. Also note which drive and connection you tested.
4. If a result looks unexpectedly low, run the test a second time under the same conditions. For an external drive, compare a direct connection with the usual hub or dock, if available.

Use the results as a comparison, not a pass or fail threshold. A hard drive, a SATA SSD, and an NVMe SSD have different expected performance. For a closer comparison, test the same drive with the same computer, port, power state, and background workload. The article on why external drives slow down through USB hubs explains why the connection can matter as much as the drive.

What the results mean

Large-file reads and writes are both slow

The drive may be limited by its type, age, connection, or current workload. An older hard drive will generally be slower than a solid-state drive, and an external drive connected through a slow port or hub may not reach its full speed. The benchmark alone cannot tell which part is responsible.

Reads are much faster than writes

This can be normal for some drives, especially during long writes or when a fast temporary write cache is exhausted. It can also happen if another process is using the drive or the drive is nearly full. Retest after the computer is idle before treating this as a fault.

Large-file speeds look reasonable, but small writes are slow

Small writes are a different kind of work from copying one large file. Weak small-write performance can contribute to pauses when opening applications or handling many small files, but it is not proof that the drive is failing. Other parts of the computer and the operating system also affect those tasks.

Results change a lot between runs

That points first to changing test conditions, such as a backup, update, antivirus scan, heat, or a background download. A browser benchmark can also vary between runs. Repeat it when the computer is idle and compare results only from similar conditions.

How to check a low or uneven result

1. Let other disk activity finish. Pause file transfers, cloud sync, backups, and large downloads. Restart the computer if you cannot identify what is using the drive, then wait for startup activity to settle before testing again.
2. Check the connection. For an external drive, connect it directly to the computer instead of through a hub or dock. Try a different cable and port. A connector that fits does not guarantee that the port supports the drive's fastest interface.
3. Check available space. On Windows 11, open Settings › System › Storage. On macOS, open System Settings › General › Storage. A drive with very little free space may behave differently, but do not delete the seller's or buyer's files just to improve a benchmark.
4. Keep power conditions steady. Connect a laptop to power and turn off battery-saving modes for the comparison. On Windows 11, check Settings › System › Power & battery. On macOS, check System Settings › Battery. Power settings can change system behavior, so record them if you are comparing before and after results.
5. Retest after cooling and settling. A drive that has just handled a large transfer or been under sustained load may perform differently. Let it sit idle for several minutes, then repeat the test once. Avoid running many back-to-back tests as a substitute for a drive health check.

When the drive may need attention

A low score by itself does not establish that a drive is damaged. Take it more seriously if it comes with repeated file errors, freezes while opening or copying files, disconnects, unusual clicking from a mechanical hard drive, or warnings from the operating system. Back up any important data before further checks.

For a resale check, inspect the drive's health information with the computer's operating-system tools or a diagnostic provided by the drive manufacturer. A browser test cannot read every health indicator, confirm the drive's remaining life, or certify that every stored file is intact. If health checks report errors, the drive disconnects repeatedly, or symptoms continue across known-good cables and ports, replace it or have it assessed before selling the computer. Be clear with the buyer about any unresolved problem.

What a speed test can and cannot show

A drive can be fast enough for one task and still be a bottleneck for another. Large-file speed matters for copying videos or backups, while small writes reflect a different workload. The rest of the computer, its software, and the drive interface affect real use too. A Storage Test is useful for finding clues and comparing repeatable runs, not for certifying a resale item.

The test uses temporary browser data rather than your personal files. For more context on this type of measurement, see why browser storage tests use temporary data.