External SSDs offer a number of advantages over traditional external hard drives, especially when it comes to speed. But are they still considered fast compared to internal SSDs or the latest generation of external storage devices?
How do external SSDs connect to a computer?
External SSDs connect to computers through USB, Thunderbolt, or other external interfaces. The most common connection types are:
- USB 3.2 Gen 2×2 (20Gbps)
- USB 3.2 Gen 2 (10Gbps)
- USB 3.2 Gen 1 (5Gbps)
- USB 3.0 (5Gbps)
- USB 2.0 (480Mbps)
- Thunderbolt 3 (40Gbps)
- Thunderbolt 4 (40Gbps)
Newer and faster connections like USB 3.2 Gen 2×2 and Thunderbolt 4 allow external SSDs to reach speeds closer to internal SSDs. However, you need compatible ports on your computer to take advantage of these faster technologies.
External SSD speeds compared to internal SSDs
Internal SSDs connected directly via SATA or PCIe can offer faster speeds than external SSDs. Some key speed differences:
- Internal SATA SSDs – up to 600MB/s sequential read/write
- Internal PCIe 4.0 SSDs – up to 7000MB/s sequential read/write
- External SATA SSDs – up to 550MB/s sequential read/write
- External NVMe SSDs – up to 2500MB/s sequential read/write
As you can see, the fastest external SSDs still can’t match the speeds of modern internal PCIe 4.0 SSDs. But they can come close to SATA SSD speeds.
Average real-world speeds will vary based on the drive and computer capabilities. But in general, external storage is bottlenecked somewhat by the USB or Thunderbolt interface speed limit.
Why are external SSDs slower?
There are a few reasons why external SSDs have lower speeds than internal SSDs:
- External interfaces like USB and Thunderbolt are slower than internal SATA/PCIe connections.
- Additional processing/controller hardware required for external enclosure.
- Power limitations – external SSDs may be limited by interface power delivery.
- Thermal throttling – external drives can get hot which may force speed reductions.
Do connection types affect speed?
Absolutely. The interface and supported standards determine the maximum theoretical speeds. Here are some typical real-world speeds for different connections:
|Typical Real-World Speeds
|Up to 35MB/s
|USB 3.2 Gen 1 (USB 3.0)
|Up to 350MB/s
|USB 3.2 Gen 2
|Up to 550MB/s
|USB 3.2 Gen 2×2
|Up to 1500MB/s
|Up to 2500MB/s
As you can see, older USB 2.0 and 3.0 provide a major bottleneck, while newer technologies like USB 3.2 Gen 2×2 and Thunderbolt 4 come close to maxing out the SSD performance.
Do cable lengths affect speed?
Cable length can play a role in maximum external SSD speeds. Longer cables tend to degrade the quality of data transfer signals. For optimal performance, shorter cables are ideal such as:
- USB – 3 feet or less
- Thunderbolt – Under 6 feet
That said, unless you’re using very long cables, like over 6 feet, speed differences are usually minimal. Using premium certified cables can help alleviate any reductions in speed due to cable length.
How does drive format affect speed?
External SSDs come preformatted in a variety of ways, with common formats being:
- NTFS (Windows)
- exFAT (Cross-platform)
- HFS+ (macOS)
- APFS (macOS)
In general, formatting doesn’t have a major impact on SSD speeds. But some formats like exFAT have slightly slower speeds in certain usage scenarios. NTFS and APFS are optimized for their respective operating systems.
Do enclosure materials impact speed?
The material the external SSD enclosure is made of generally doesn’t impact speeds. Most enclosures are plastic but some premium options use materials like aluminum for better aesthetics and heat dissipation.
One exception is with Thunderbolt enclosures. Because Thunderbolt uses PCIe signaling, the enclosure must be made of a non-conductive material like plastic to avoid interference. Metal Thunderbolt enclosures require special design considerations.
Are cheaper external SSDs slower?
Price isn’t necessarily an indication of SSD speeds. You can find affordable external SSDs with similar real-world speeds as more expensive models. However, cheaper options may cut corners in these areas:
- Lower-quality NAND flash memory
- Smaller cache size
- Limited number of NAND channels
- Older generation USB/Thunderbolt controller
- Slower sustained write speeds
So in certain usage cases, like large file transfers or HD video editing, cheaper SSDs may show their weaknesses. But for everyday use, an entry-level external SSD can still provide decent performance.
Do SSD sizes and capacity impact speed?
An SSD’s physical size doesn’t directly affect speed, but the internal configuration and capacity does play a role. Higher capacity SSDs generally have better parallelism allowing for faster speeds:
- More NAND flash chips
- Extra NAND channels
- Larger dynamic cache sizes
Smaller external SSDs tend to use fewer NAND chips and channels. This is noticeable on sustained workloads like big file transfers.
Are portable external SSDs slower?
Portable and pocket-sized external SSDs connect via the same interfaces as larger SSDs. But they often have lower rated speeds. Reasons for this include:
- Lower power limits of USB ports on mobile devices
- Space constraints allowing for fewer NAND chips
- Thermal throttling due to small size and heat dissipation challenges
For quick transfers and basic use, portable SSD speeds are still adequate. But expect lower performance especially when moving large files.
Do Thunderbolt 4 SSDs offer speed advantages over Thunderbolt 3?
Thunderbolt 4 is the latest iteration of Intel’s Thunderbolt protocol. It offers some speed enhancements over the previous Thunderbolt 3 standard:
- Double bandwidth for video – Up to 8K at 60Hz (Thunderbolt 3 supports 4K at 60Hz)
- Minimum performance spec of 3,000MB/s (Thunderbolt 3 minimum is 1,250MB/s)
In real-world usage though, Thunderbolt 3 and 4 SSD speeds are fairly comparable, with both achieving over 2000MB/s. Thunderbolt 4’s benefits are mainly seen with demanding workloads like 8K video editing.
Do NVMe SSDs offer faster Thunderbolt speeds?
Thunderbolt 3 and 4 can both accommodate NVMe SSDs which leverage PCIe bandwidth for faster speeds compared to SATA SSDs. Most high-performance Thunderbolt external SSDs now use NVMe technology.
NVMe SSDs paired with Thunderbolt 3/4 can reach over 2500MB/s. So for maximal Thunderbolt speeds, NVMe is preferred, although SATA SSDs still perform decently.
Can external SSD speeds slow down over time?
Like all SSDs, external solid state drives can exhibit slower speeds over time. This is especially true for drives used intensively for writes and rewrites. Reasons include:
- Wear on NAND flash cells
- Increased bit errors
- Block reallocation processes
- Thermal throttling from heat buildup
- Fragmentation of data
That said, thanks to TRIM, wear leveling, and garbage collection, most external SSDs maintain their fast speeds for many years with minimal degradation. Heavy workloads may eventually impact performance.
Does disk fragmentation affect external SSDs?
Disk fragmentation happens on external SSDs when data written is distributed across many locations. This leads to inefficient read times.
While fragmentation does occur, SSDs are far less prone to performance degradation than traditional hard drives. TRIM, wear leveling, and the absence of physical seek head movement lessen the impact compared to a fragmented HDD.
Regardless, periodically defragmenting your external SSD when connected to a Windows PC can optimize and restore peak speeds.
How can external SSD speeds be boosted further?
If you want to push external SSD speeds to the limit, here are some tips:
- Use USB 3.2 Gen 2×2 or Thunderbolt 4 for fastest interface speeds
- Get an enclosure with active cooling to prevent thermal throttling
- Enable UASP support on USB connections for added performance
- Utilize RAID 0 configurations for even faster read/write speeds
Upgrading your computer to support the latest USB or Thunderbolt standards makes the most significant impact for maximum external SSD performance.
While internal SSDs connected directly via PCIe or SATA remain the speed kings, external SSD speeds are still very fast. Models leveraging high-speed interfaces like USB 3.2 Gen 2×2 and Thunderbolt 4 can reach performance near the limits of the drive itself.
For most users, even entry-level external SSDs provide plenty of speed boost over traditional hard drives. And when compared to flash drives, external SSDs are in a different performance league entirely.
While not quite as fast as internal SSDs, external solid state drives provide portable and versatile storage with impressive real-world speeds. As connection technologies continue to evolve, external SSD speeds will only get faster.