In the opening paragraphs, we’ll provide quick answers to some common questions about internal vs external SSD speeds:
Is an external SSD as fast as an internal SSD?
Generally no – an internal SSD is usually faster than an external SSD connected via USB or Thunderbolt. However, high-end external SSDs with Thunderbolt 3 or USB 3.2 Gen 2×2 can reach speeds comparable to internal SSDs.
Why are internal SSDs faster?
Internal SSDs connect directly to the PCIe bus and don’t have to go through the inherent bottlenecks of external connections like USB or Thunderbolt. The PCIe bus offers much higher bandwidth potential than external ports.
When is an external SSD as fast as internal?
Top-tier external SSDs using cutting edge interfaces like Thunderbolt 3 or USB 3.2 Gen 2×2 can nearly match the speeds of a PCIe Gen3 internal SSD. For example, the Samsung X5 Thunderbolt 3 SSD can reach read/write speeds of up to 2,800/2,300 MB/s.
What speeds can I expect from an external SSD?
Most external SSDs with USB 3.2 Gen 2 can reach 500-1000 MB/s. USB 3.2 Gen 2×2 can hit 2000+ MB/s. Thunderbolt 3 external SSDs commonly reach 1700-2800 MB/s. But there are many factors that affect real-world speeds.
Does the external SSD enclosure affect speed?
Yes, a higher quality external SSD enclosure with better cooling, components, firmware, and materials can positively impact sustained performance, consistency, and endurance.
Conclusion
In summary, while internal SSDs are generally faster than external, high-end external SSDs are reaching similar speeds by utilizing the latest in high bandwidth interfaces like Thunderbolt 3 and USB 3.2 Gen 2×2.
Internal vs External SSD Speed Comparison
To understand the speed differences in more detail, let’s compare some real-world internal and external SSDs across various interfaces like SATA, USB, and Thunderbolt:
SATA SSDs
SATA SSDs connected via the SATA III interface are limited to sequential read/write speeds of around 500-550 MB/s. This interface bottleneck applies to both internal and external SATA SSDs.
External SSDs – USB 3.2 Gen 1
Many external SSDs use the common USB 3.2 Gen 1 interface, which offers maximum theoretical bandwidth of 5 Gbps (625 MB/s). Real-world speeds end up around 400-500 MB/s sequential read/write for these entry-level external SSDs.
External SSDs – USB 3.2 Gen 2
Faster external SSDs utilize the 10 Gbps USB 3.2 Gen 2 interface for double the bandwidth. Expect real-world speeds around 800-900 MB/s sequential read/write from USB 3.2 Gen 2 external SSDs.
External SSDs – USB 3.2 Gen 2×2
Leading edge external SSDs are starting to leverage 20 Gbps USB 3.2 Gen 2×2 for even faster transfer rates. These SSDs can reach impressive speeds over 1,400 MB/s read and 1,000 MB/s write.
External SSDs – Thunderbolt 3
Top of the line external SSDs use Thunderbolt 3 and direct PCIe connectivity for massive 40 Gbps bandwidth. Real-world speeds for Thunderbolt 3 external SSDs range from 1,700 MB/s on the low end to 2,800 MB/s from high-performance models.
M.2 NVMe Internal SSDs
Cutting-edge internal M.2 NVMe SSDs mounted directly on the PCIe bus offer the fastest interface for SSDs. Current PCIe 3.0 x4 M.2 drives can theoretically hit 4,000 MB/s, while new PCIe 4.0 models are pushing 5,000 MB/s.
Internal vs External SSD Example Speed Comparison
| SSD Type | Interface | Sequential Read | Sequential Write |
|---|---|---|---|
| SATA SSD | SATA III | 550 MB/s | 520 MB/s |
| Ext. SSD USB 3.2 Gen 1 | USB 3.2 Gen 1 | 500 MB/s | 400 MB/s |
| Ext. SSD USB 3.2 Gen 2 | USB 3.2 Gen 2 | 900 MB/s | 850 MB/s |
| Ext. SSD USB 3.2 Gen 2×2 | USB 3.2 Gen 2×2 | 1,400 MB/s | 1,000 MB/s |
| Ext. SSD Thunderbolt 3 | Thunderbolt 3 | 2,800 MB/s | 2,300 MB/s |
| M.2 NVMe PCIe 3.0 SSD | PCIe 3.0 x4 | 3,500 MB/s | 2,500 MB/s |
This table compares real-world sequential read and write speeds across common internal and external SSD interface options. Top performing Thunderbolt 3 and USB 3.2 Gen 2×2 external SSDs are getting close to internal M.2 NVMe PCIe 3.0 SSD read/write performance.
Factors That Affect External SSD Speed
There are many factors beyond just the interface that affect real-world speeds and performance of an external SSD:
SSD Components
The NAND flash memory chips, SSD controller, and DRAM cache used in the external SSD determine the maximum drive performance. Higher grade components generally deliver faster speeds, lower latency, and better endurance.
SSD Controller & Firmware
The SSD controller and firmware manage all data transfer operations. A more advanced controller with optimized firmware can achieve faster real-world transfer rates and maximize interface bandwidth utilization.
External Enclosure
The design and construction of the external SSD enclosure impacts performance. Enclosure cooling, materials, interface chipset, and PCB layout all affect the SSD’s sustained speeds and thermal throttling behavior.
Thunderbolt vs USB Controller
Thunderbolt 3 connectivity relies on Intel’s Alpine Ridge controller, while USB ports use ASMedia or VIA Labs controllers. The Thunderbolt controller in particular is tuned for maximum SSD performance.
PCIe vs USB Bridge
NVMe SSDs require a bridge chip to translate PCIe to USB. More efficient PCIe-USB bridge designs minimize translation overhead and keep USB performance high.
USB or Thunderbolt Cable
Lower quality cables can degrade signal integrity at high data transfer speeds. Active cables, proper shielding, and short cable lengths help maximize interface bandwidth.
USB or Thunderbolt Port
The specific USB or Thunderbolt port on a PC impacts maximum speeds. For example, Thunderbolt 3 ports connected to the PCH tend to have lower bandwidth than ports directly wired to the CPU.
Host Computer Workload
Background processes on the host PC can consume interface bandwidth and controller resources, resulting in lower external SSD performance.
Comparing Thunderbolt 3 vs USB 3.2 Gen 2×2
Thunderbolt 3 and USB 3.2 Gen 2×2 (20 Gbps) are the fastest universal cable interfaces used for external SSDs today. But which one is better for an external SSD?
Speed
Thunderbolt 3 has more theoretical bandwidth at 40 Gbps compared to 20 Gbps for USB 3.2 Gen 2×2. In real-world use, Thunderbolt 3 SSDs consistently outperform USB 3.2 Gen 2×2 models.
Power Delivery
Thunderbolt 3 provides up to 100W of power delivery. This allows safer charging of connected devices like laptops. USB 3.2 Gen 2×2 is limited to 60W.
Display Support
Thunderbolt 3 can output single 5K or dual 4K displays using one cable. USB 3.2 Gen 2×2 has no display capabilities.
PCIe Access
Thunderbolt 3 provides direct access to the PCIe bus. This allows external GPUs and other PCIe devices to connect via Thunderbolt. USB does not provide any PCIe connectivity.
Cables
Active Thunderbolt 3 cables can extend up to 60 meters. USB 3.2 Gen 2×2 passive cables are limited to just 2 meters before signal degradation.
Adoption
USB ports have near universal adoption across PCs and devices. Thunderbolt 3 use is still limited to Apple and high-end Windows laptops.
Controllers
Thunderbolt 3 uses Intel controllers carefully optimized for SSD performance. The USB ecosystem has more fragmented controller support.
Cost
Thunderbolt 3 cables and accessories generally have a price premium over USB counterparts.
Thunderbolt 3 vs USB 3.2 Gen 2×2 Comparison Table
| Specification | Thunderbolt 3 | USB 3.2 Gen 2×2 |
|---|---|---|
| Max Bandwidth | 40 Gbps | 20 Gbps |
| Power Delivery | Up to 100W | Up to 60W |
| Display Support | Single 5K or dual 4K | None |
| PCIe Access | Yes | No |
| Max Cable Length | 60m (active) | 2m (passive) |
| Adoption | Moderate | Ubiquitous |
| SSD Performance | Higher | Slightly lower |
| Cost | Higher | Lower |
In summary, Thunderbolt 3 wins out in terms of pure performance, power delivery, display support, and PCIe access. But USB 3.2 Gen 2×2 has the advantages of wider adoption and lower costs.
Real-World External SSD Benchmarks
Let’s compare real-world test results from some of the top performing external SSDs available today:
Samsung X5 Thunderbolt 3 SSD
- Sequential Read Speed: 2,800 MB/s
- Sequential Write Speed: 2,300 MB/s
- Random Read Speed: 320,000 IOPS
- Random Write Speed: 330,000 IOPS
With its blazing Thunderbolt 3 speeds, the Samsung X5 is one of the fastest portable SSDs available. The X5 delivers sequential transfers over 2.5 GB/s and IOPS performance over 300,000.
SanDisk Extreme Pro NVMe USB SSD
- Sequential Read Speed: 1,050 MB/s
- Sequential Write Speed: 1,000 MB/s
- Random Read Speed: 300,000 IOPS
- Random Write Speed: 275,000 IOPS
The SanDisk Extreme Pro demonstrates the performance potential of high-end USB 3.2 Gen 2×2 SSDs. It has excellent sequential transfer rates over 1 GB/s and consistency at queuing multiple operations.
Samsung T7 Touch USB 3.2 Gen 2 SSD
- Sequential Read Speed: 1,050 MB/s
- Sequential Write Speed: 1,000 MB/s
- Random Read Speed: 240,000 IOPS
- Random Write Speed: 260,000 IOPS
Samsung’s USB 3.2 Gen 2 SSD shows how regular 10 Gbps Gen 2 SSDs still deliver impressive real-world performance with 1 GB/s sequential speeds and over 240,000 IOPS random performance.
WD My Passport External HDD
- Sequential Read Speed: 174 MB/s
- Sequential Write Speed: 168 MB/s
- Random Read Speed: 1,975 IOPS
- Random Write Speed: 1,825 IOPS
For comparison, a SATA-based external hard drive like the WD My Passport is significantly slower. Sequential transfers are below 200 MB/s and random IOPS performance is around 2,000.
Maximizing External SSD Performance
There are some steps you can take to ensure your external SSD interface performs at its full potential speed:
Use a Higher Capacity SSD
Higher capacity SSDs generally have more NAND flash chips and controller channels. This results in improved parallelism and speed, especially for queued workloads.
Get an Efficient External Enclosure
Carefully research external SSD enclosures, as design factors like cooling can impact sustained performance.
Utilize UASP Drivers
UASP drivers reduce protocol overhead and queue commands more efficiently over USB for better utilization of interface bandwidth.
Plug SSD into Rear Motherboard Ports
Rear motherboard USB and Thunderbolt ports typically offer better performance than front case ports.
Avoid Bus-Powered Drives
Bus-powered external SSDs can experience intermittent power limitations under load. Use an SSD with a dedicated power adapter for full performance.
Upgrade your Computer Hardware
Newer motherboards and CPUs provide the latest USB 3.2 Gen 2×2 and Thunderbolt 3 ports for fastest interface speeds.
Conclusion
While internal SSDs generally outperform external SSDs, high-end external SSDs are reaching similar real-world speeds by leveraging cutting edge interface technology like Thunderbolt 3 and USB 3.2 Gen 2×2. Carefully matching your external SSD with the appropriate interface and computer hardware maximizes the performance potential.
