When it comes to storage devices, read and write speeds are important factors to consider. The read speed determines how fast data can be accessed from the storage device, while the write speed determines how quickly new data can be saved to the device. In this article, we will examine what constitutes a good read and write speed across different types of storage devices.
What is Read and Write Speed?
Read and write speed refers to the speed at which data can be read from or written to a storage device. It is measured in megabytes per second (MB/s) or gigabytes per second (GB/s).
Read speed measures how fast data can be retrieved and accessed from the storage device. For example, if you want to open a file stored on an SSD drive, the read speed determines how quickly the drive can access that file data and load it for use.
Write speed measures how quickly new data can be saved and written to the storage device. For example, if you want to save a large video file to your hard drive, the write speed determines how fast the drive can accept and save all that data.
Factors Affecting Read and Write Speed
There are several technical factors that affect the read and write speed capabilities of a storage device:
- Interface – The interface between the device and computer impacts speed. SATA, PCIe NVMe, and USB have different bandwidths.
- Memory technology – Whether the device uses spinning platters, flash memory, or other technologies affects speed.
- Memory Density – Higher density SSDs and HDDs allow for faster speeds.
- Controller – More advanced controllers manage I/O requests faster.
- Caching – Cache size and algorithms also affect overall throughput.
- Benchmark workload – Speeds vary based on different read/write patterns.
In general, solid state drives (SSDs) offer faster read and write speeds than traditional hard disk drives (HDDs). However, high performance HDDs can still outpace lower-end SSDs. The interface and controller are also key factors.
Average Read and Write Speeds by Device
Here are the typical sequential read and write speeds you can expect from different storage devices:
Hard Disk Drives (HDD)
|HDD Type||Read Speed||Write Speed|
|5400 rpm HDD||100 MB/s||70 MB/s|
|7200 rpm HDD||150 MB/s||100 MB/s|
|10,000 rpm HDD||200 MB/s||150 MB/s|
|15,000 rpm HDD||250 MB/s||200 MB/s|
HDD speeds range from 100-250 MB/s depending on the rotational speed. Faster drives have higher rpm. But HDDs are still limited by mechanical moving parts.
Solid State Drives (SSD)
|SSD Type||Read Speed||Write Speed|
|SATA SSD||500 MB/s||350 MB/s|
|PCIe NVMe SSD (Gen 3)||3,500 MB/s||2,500 MB/s|
|PCIe NVMe SSD (Gen 4)||7,000 MB/s||5,000 MB/s|
SSDs can deliver blazing fast speeds, ranging from 500 MB/s on basic SATA drives up to 7,000 MB/s for high-end PCIe NVMe Gen 4 SSDs.
|External Device||Read Speed||Write Speed|
|USB flash drive||200 MB/s||40 MB/s|
|SD card||100 MB/s||20 MB/s|
|USB HDD||120 MB/s||120 MB/s|
|External SSD (USB 3.2)||1,000 MB/s||1,000 MB/s|
|External SSD (Thunderbolt 3)||2,750 MB/s||2,750 MB/s|
External and removable storage tends to have lower bandwidth ceilings based on the interface, but Thunderbolt 3 external SSDs can match internal PCIe speeds.
Minimum Read and Write Speed Recommendations
So what read and write speeds are considered good? The minimum speed recommendations depend on your use case:
Operating System Drive
For an OS drive, a minimum of 100 MB/s sustained read and write speeds are recommended. This ensures fast boot times and responsive system performance.
For PC gaming storage, a solid state drive with at least 500 MB/s sequential read and write speeds is recommended. This enables fast loading textures and assets.
For creative workflows like video editing, 3D modeling, and CAD, opt for PCIe NVMe SSDs with over 2,500 MB/s sustained speeds. This enables smooth workflow.
For external storage, USB 3.2 and Thunderbolt 3 interfaces are preferred. Aim for at least 400 MB/s reads and writes to prevent bottlenecks.
IOPS for Random Read/Write Speeds
In addition to sequential speeds, random read/write speeds impact responsiveness. These are measured in input/output operations per second (IOPS):
- HDDs offer 100-200 IOPS for random reads and writes.
- SATA SSDs deliver 10,000 to 100,000 IOPS.
- High-end PCIe NVMe SSDs exceed 400,000 IOPS.
If your use case involves lots of small file operations, choose a high IOPS SSD for optimal performance.
Factors That Affect Real-World Speeds
While those speeds look impressive on spec sheets, real-world speeds are affected by:
- File size – Larger files sustain higher sequential speeds.
- Queue depth – Drives handle multiple I/O requests in parallel.
- Interface overhead – Protocols like SATA and USB add processing delays.
- File system – Some file systems manage data better than others.
- Encryption – Security adds encryption/decryption overhead.
Real-world speeds tend to be around 20-30% lower than advertised sequential speeds after accounting for these factors. Still, GUIDs like write to at least 1600 IOPS per user, 35x average IOPs to max IOPs, and 30 MB/s per logged in user are useful rules of thumb for practical speeds.
Benchmarking Read and Write Speeds
To test real-world speeds, you can benchmark your drives using tools like:
- CrystalDiskMark – Quickly tests sequential and random speeds.
- AS SSD Benchmark – Provides in-depth info and scoring.
- Anvil’s Storage Utility – Comprehensive benchmarks and comparisons.
- BlackMagic Disk Speed Test (Mac) – Simple but effective Mac benchmark.
These benchmarks will measure the actual sustained read and write speeds your drives can deliver on your system. This helps validate if the drives meet your performance requirements.
Tips to Improve Read and Write Speeds
If your storage devices are underperforming, here are some troubleshooting tips:
- Update SSD firmware – Flash new firmware for bug fixes and optimizations.
- Install latest chipset drivers – Get the newest SATA/NVMe drivers.
- Adjust power settings – Disable power saving modes that throttle speeds.
- Activate write cache – Enable drive write cache for faster writes.
- Secure erase SSDs – Completely wipe drives to restore performance.
- Defragment HDDs – Consolidate fragmented data.
Properly configuring your system can help storage devices achieve their advertised peak read and write speeds.
Faster read and write speeds ensure snappier performance and quicker workflows when working with large files or applications. While HDDs are cheaper, SSDs are up to 5-10x faster thanks to lack of moving parts.
For most desktop users, a SATA SSD with at least 500 MB/s read/write speeds is recommended for OS and primary storage. Creative pros benefit from even faster PCIe NVMe SSDs exceeding 2,500 MB/s. External storage should use USB 3.2, Thunderbolt 3, or eSATA to prevent interface bottlenecks.
Benchmark your drives and optimize your setup to take full advantage of the speeds your storage devices are capable of. Investing in fast storage pays dividends through more productive and frustration-free computing.