External SSDs vs Internal SSDs: Which is Faster?

No matter what system you have, inevitably the time comes when you run out of storage. There has never been a better time to upgrade from a hard disk drive (HDD) to a solid state drive (SSD) or upgrade to a larger SSD. Portable and internal SSDs have become larger, faster, and more affordable. But which is best for you: an internal or external SSD? And which is faster?

If you haven’t already done so, there are ways to increase computer storage space. It often can help the speed of your drive and we are, after all, here to talk about speed. Consider these Crucial SSDs when comparing speeds and performance:

SSD Form Factors

For internal SSDs there are three primary form factors: 2.5-inch, M.2, and mSATA. External SSDs such as the Crucial X8 and X6 portable SSD, are universally compatible with a wide range of devices and designed to interface with a cable.

Internal SSDs form factors

2.5-Inch SSD

The standard form factor for many years has been the 2.5-inch such as the MX500, which fits inside the drive bay of both laptop and desktop computers. Because many users replace their hard drives with solid state drives, the 2.5-inch drive has become a standard for all HDDs and SSDs. They are designed to minimize the need to replace the connecting interface cables, making the transition to a higher performance drive as easy as possible.


The smallest form factor for SSDs is called M.2, which is about the size of a stick of gum. M.2 SSDs such as the Crucial P2 attach to the motherboard via an M.2 socket and are designed for space-constrained tablets and ultrabooks. M.2 typically have the highest read and write speeds due to their interface. M.2 can interface either through PCIe or SATA, some motherboards have slots for one or both.


The mSATA form factor SSD is one-eighth the size of a 2.5-inch drive and are designed to plug into an mSATA socket on a system’s motherboard. mSATA drives are used in ultra-thin and mini devices, or as a secondary drive in desktops.

External SSD form factor

External SSD

Portable SSDs such as the Crucial X8 and X6 are designed using the same technology as a 2.5-inch, mSATA, or M.2 with an added enclosure and cable interface. Portable drives can increase storage capacity for nearly any computer, tablet, phone, or console. The X8 works with Windows, Mac, iPad Pro, Chromebook, Android, Linux, and even game consoles such as PS4 and Xbox.

SSD Interface

Knowing the type of SSD is just as important as knowing the way in which the SSD interfaces or connects with the system. Although there are a fair number of different interfaces, we're going to look at SATA and PCIe® for internal SSDs and USB and Thunderbolt for portable SSDs.

Serial ATA (SATA)

The most common SSD interface, commonly used with 2.5 drives. Affords the convenience of interoperability with SATA-based HDDs. SATA interface is older than PCIe, but when it was first developed, it brought important advances to computing, such as hot swapping abilities or changing drives quickly. SATA for storage drives was developed for hard drives. When solid state drives came on the market, they adopted the same interface so users could easily upgrade their storage drive. The latest generation provides transfer rates of up to 6GB/s. SATA uses Advanced Host Controller Interface (AHCI) command protocols which were designed for mechanical HDDs.

PCI Express ® (PCIe)

PCIe, also known as PCI Express® or Peripheral Component Interconnect Express, is a newer high-speed serial bus interface that features a smaller physical footprint. PCIe is a physical connection that transmits information and data from one device to another within the computer or between the computer and a peripheral piece of equipment. The implementation of multiple lanes for the PCIe connection is one of the most important features of the standard. A lane is a single serial data connection, similar to a SATA connection. PCIe uses four lanes for storage devices, resulting in data exchange that is four times faster than a SATA connection. PCIe is used with M.2 SSDs.

What is NVMe, and why is it important to PCIe?

NVMe, NVM Express™, or Non-Volatile Memory Host Controller Interface Specification, is a communication protocol designed specifically to work with flash memory using the PCIe® (PCI Express®) bus. It was created to take advantage of the parallel nature of solid state drives. Combined with the PCIe bus and the increased read and write speeds of NAND technology, the NVMe protocol creates faster non-volatile storage. The combination of the NVMe protocol and the PCIe connection with an SSD results in read and write speeds that are 4x faster than a SATA SSD with a SCSI protocol.


Almost every computer today has a USB connection, thus making it the ideal interface today when you use your drive on multiple computers or devices. The USB connector your device utilizes directly affects transfer speeds such as type A or type C. Obviously aging USB-A interfaces are slower than newer USB-C. The Crucial X8 portable SSD can reach the following transfer speeds using various connections.

Host compatibility


Thunderbolt 3 - 40 Gb/s

USB 3.1 Gen 2- 10 Gb/s

USB 3.1 Gen 1 - 5 Gb/s


USB 3.1 Gen 1 - 5 Gb/s

USB 3.0 - 5 Gb/s

USB 2.0 - 480 Mb/s That can support 5V


Thunderbolt is an interface connection designed between Intel® and Apple® designed to connect peripherals to computers. The latest generation Thunderbolt 3 is unique due to sharing the same reversable port as a USB-C and having backwards compatibility. USB-C accessories and cables will work with a Thunderbolt 3 port, but not all Thunderbolt 3 devices will work in a USB-C port.

How to speed up your existing SSDs

Several other factors can contribute to the speed of your SSD. Storage, firmware, trim, and tracking the health of your drive can help keep your SSD running fast.

  1.  Its best to keep 10-15 percent of your drive free to balance performance and storage. Writing speeds can directly be affected if your drive is near or at its full capacity.
  2.  Keeping your firmware updated helps your SSD run at peak performance and ensures technical issues are corrected.
  3.  All Crucial SSDs are designed and tested with the assumption that trim will be used on the computer’s operating systems, however not all operating systems support trim, and that’s ok. If your system doesn’t support trim, think about upgrading to one that does.
  4.  Use a self-monitoring, analysis, and reporting technology (SMART) system such as Storage Executive to track the health of your Crucial X8 portable SSD.


So, which is faster? The answer really is: it depends. It depends on your system, and its form factor and interface. While the latest external SSDs have incredible write speeds, they cannot reach those speeds using older connections such as USB-A. Likewise, drive speeds are directly affected by the interface. The speed will also differ if you pair an M.2 with PCIe or SATA. By comparing the performance of an M.2/PCIe/NVMe drive to a 2.5-inch mSATA or an external drive, you will also find variations in speed.

The most important aspect to consider is which form factor and interface is installed on your computer. It can be difficult to tell the difference between a PCIe and a SATA connection if you look at the slot on the motherboard. Check your computer specifications to see which interface and form factor your computer supports. You can also use the Crucial System Advisor™ or System Scanner to find a compatible part and interface.

In the end, there are many factors that determine which is faster. Ultimately, you can pair an external SSD with an internal SSD and have the best of all worlds. Fast, portable, compatible storage that works with a wide range of systems in the form of an external SSD, and a computer with the latest internal SSD running your system. You can’t have too much, upgrading the type and capacity of storage on your computer and devices is ultimately the right answer.