Connecting an external drive to a smartphone or tablet has become commonplace, but users are often faced with an unpleasant surprise: copying movies takes hours, and launching applications from a memory card occurs with a noticeable delay. The reason for this is not only the USB interface, but also the actual throughput of the drive itself, which may differ significantly from what is stated on the packaging. Many budget flash drive models have low random access speeds, which is critical for the operation of the operating system Android.
To understand whether a particular drive is worth using for memory expansion or backup, it is necessary to conduct objective benchmarking. There are several methods for assessing performance: from using specialized mobile utilities to connecting the device to a personal computer for more detailed analysis. Sequential reading speed and recordings are just the tip of the iceberg; for comfortable work, indicators IOPS (input/output operations per second) are more important when working with small files.
In this article we will look at how to accurately measure these parameters, which applications are trustworthy and how to interpret the obtained numbers. You will learn why the same flash drive can show different results on different devices and how to avoid buying a fake with underrated characteristics. Correct diagnostics will help save time and nerves when working with large volumes of data.
Why you need to test the speed of a USB drive
The main reason for conducting tests is to check whether the stated characteristics correspond to real indicators. Manufacturers often indicate the maximum read speed achieved under ideal laboratory conditions, but are silent about the write speed, which is usually 3-5 times lower. If you plan to record high-resolution video on a flash drive or make system backups, low recording speed will become the bottleneck of the entire procedure.
In addition, testing can identify problems with the memory controller or physical wear of NAND cells. Over time, the storage resource is depleted, and the rate of degradation may be uneven. A sharp drop in performance after filling a certain amount of data often indicates that SLC cache is full and the controller cannot cope with the flow of information.
⚠️ Attention: If the write speed drops to several kilobytes per second after filling 10-20% of the volume, this is a clear sign of use low-quality memory cells or a fake controller that cannot provide a stable data flow.
Checking is also necessary before purchasing a new flash drive, if it is possible to test a demo sample in a store. This will help weed out frankly slow models that will slow down your smartphone when you try to install applications or games on them. For Android devices, the speed of working with small files (4K Random Read/Write) is especially critical, since the system constantly accesses the disk to load configs and cache.
Preparation of the device and drive for tests
Before starting measurements, it is necessary to ensure stable operating conditions in order to exclude influence of third-party factors on the result. First of all, check the port USB of your smartphone: it should be working properly and provide sufficient power. Some older phone models cannot supply the required current for fast drives, which leads to speed throttling.
It is recommended to first clear the drive being tested of unnecessary files or format it. Having a large amount of fragmented data can skew test results, especially in sequential write scenarios. The file system also plays a role: for modern devices, the optimal choice would be exFAT or NTFS (if driver support is available), since the outdated one FAT32 has limitations and less efficiency.
☑️ Preparation for testing
It is important to make sure that heavy processes are not running on your smartphone, such as downloading updates, synchronizing cloud storage, or rendering video. Any background activity loads the processor and data bus, which will inevitably reduce benchmark performance. It is best to switch the device to Do Not Disturb mode and turn off wireless interfaces if they are not directly involved in the testing process.
Using specialized mobile applications
The easiest and most affordable way to check the speed is to install a specialized application directly from the store Google Play. There are many utilities that conduct a series of tests and provide visual results in the form of graphs and numbers. Among the market leaders are A1 SD Bench, AndroBench and CPDT (Cross Platform Disk Test).
The testing process in such applications is usually standardized: the app writes a file of a certain size (for example, 1 GB) to disk and then reads it back, measuring the operation time. More advanced tools such as AndroBenchalso test SQLite database speed and random 4KB file access, giving a complete picture of storage performance.
- 📱 A1 SD Bench: A simple application that supports testing internal memory and external cards via OTG. Allows you to save and share results.
- 🚀 AndroBench: Provides detailed sequential and random read/write data, as well as database tests. The interface may seem overloaded to beginners.
- 💾 CPDT: a cross-platform test, the results of which can be easily compared with the performance of other devices (iOS, Linux), since the methodology is the same.
When starting the test, be sure to select the path to your external flash drive in the application settings, and not the internal memory of your smartphone. By default, many utilities test the built-in drive. After completion, you will see a table with the results, where the key parameters will be Sequential Read and Sequential Write. For UHS-I memory cards, reading values from 80 to 90 MB/s are considered normal.
Before running the test in the application, close all other apps through the recent tasks menu to free up RAM and CPU time for the benchmark.
Analyzing results: reading, writing and IOPS
Having received numbers on the screen, many users are lost in their interpretation. Understanding the difference between the types of operations will help you really evaluate the quality of the drive. Sequential Read shows how quickly a flash drive can transfer a large file, for example, a movie or an archive with photos. This is an important parameter for media consumption.
However, for installing applications and operating the system, Random Read small blocks of data are much more important. The operating system Android consists of thousands of small files, and if the flash drive processes them slowly, the interface will slow down and apps will take a long time to load. The parameter IOPS (Input/Output Operations Per Second) precisely reflects the number of such operations per second.
| Operation type | Description | Impact on work | Good indicator (USB 3.0) |
|---|---|---|---|
| Seq. Read | Reading large files in a row | Watching videos, copying movies | > 100 MB/s |
| Seq. Write | Writing large files in a row | Saving backups, shooting videos | > 60 MB/s |
| 4K Read | Reading small files (4 KB) | Loading OS, launching applications | > 15 MB/s |
| 4K Write | Write small files (4 KB) | Saving settings, caching | > 5 MB/s |
If the random write performance (4K Write) is below 2-3 MB/s, use such a flash drive to install applications (adb shell pm install) is strictly not recommended. The system will constantly wait for I/O operations to complete, which will lead to noticeable lag. In this case, it is better to use the drive only as “cold” storage for documents and media files.
High sequential read speed does not guarantee fast application performance; a key parameter for system performance is the random access speed (4K Random Read/Write).
Testing via connection to a PC
To obtain the most accurate and independent results, it is recommended to connect a flash drive to a computer. Smartphones may limit speed due to the implementation of the USB controller or driver software. On a PC you can use professional software, such as CrystalDiskMark or AS SSD Benchmark.
Connect the drive via a high-quality OTG cable to the port USB 3.0 (usually blue) on your computer. Launch the app and select the drive letter corresponding to your flash drive. In the test settings, select a file size of 1 GB and a number of runs of 3-5 to average the result. This will level out random speed jumps.
⚠️ Attention: Make sure that you are testing an external drive and not the computer’s system drive. An error in disk selection can lead to unpredictable system behavior or data loss when trying to format.
The advantage of PC testing is the ability to analyze speed degradation in detail. Some apps allow you to fill the disk 50% or 90% with data and see how performance changes. This is critical for identifying flash drives with volume emulation or slow TLC/QLC memory without effective caching.
Why are the results on a PC and a phone different?
The difference is due to the bandwidth of the USB port on the smartphone (often USB 2.0 even in modern mid-range models) and the overhead of the Android file system when working through the layer compatibility.
USB interface problems and compatibility
Even the fastest flash drive will not reach its potential if the connection interface is a bottleneck. Most budget and mid-segment smartphones are equipped with standard USB 2.0ports, the maximum theoretical speed of which is 480 Mbit/s (about 60 MB/s in practice). Connecting a standard drive USB 3.1 to such a port will limit the speed precisely by the value of the port.
In addition, the quality of the OTG adapter or cable itself plays a significant role. Cheap adapters with thin wires can cause a voltage drop, which forces the flash drive controller to reduce operating frequencies to stabilize the power. This manifests itself in the form of unstable test results: today 40 MB/s, and tomorrow 15 MB/s.
- 🔌 Cable length: the longer the wire, the higher the resistance and the likelihood of signal loss. For tests, use the shortest possible cables.
- ⚡ Power: if the flash drive has an LED indicator, make sure it lights up brightly and does not blink during operation, which may indicate a lack of current.
- 📱 Drivers: some smartphones require the mode to be turned on OTG in the settings (
Settings → Additional functions → OTG), otherwise power will not be supplied to the port.
It is also worth considering the file system. If the flash drive is formatted in NTFS, and the smartphone does not have built-in drivers for recording to this system (often found in pure Android), then recording may be impossible or carried out through software crutches at low speed. In such cases, it is better to use a universal one exFAT.
Frequently asked questions and problems (FAQ)
Why is the write speed much lower than the read speed?
This is a normal situation for flash memory. The write process requires more complex operations on the controller and memory cells, including clearing blocks before writing new data. In addition, manufacturers more often advertise reading speed as the main characteristic.
Is it possible to speed up a flash drive by formatting?
Partly yes. Formatting into larger cluster sizes (for example, 64 KB instead of 4 KB) may improve the sequential writing speed of large files, but will reduce space efficiency when storing many small documents. A large cluster size is better suited for video.
The test shows a speed of 5-10 MB/s, although the USB 3.0 flash drive. What is the reason?
Most likely, you connected the device to the USB 2.0 port on your smartphone or are using a low-quality cable. It is also possible that the flash drive itself is a fake with a reflashed controller that reports incorrect characteristics to the system.
Does the remaining space on the flash drive affect the speed?
Yes, it does significantly. When free space runs out, the controller has a harder time finding empty blocks to write to and must perform Garbage Collection operations more often. It is recommended to keep at least 15-20% of the drive capacity free to maintain high performance.
How to check a flash drive without installing applications?
You can use a file manager with a copy function. Copy a large file (video) from the internal memory to a flash drive and note the time. Divide the file size in megabytes by the time in seconds to get the approximate write speed. However, this method is less accurate than specialized benchmarks.