Thought Leadership

November 1, 2017
SSDs, USB Drives, SD Memory Cards: Know the Difference
Choosing the right storage option for the right application

By: Keith Tsai

Gone are the days when consumers and businesses had to use unwieldy floppy disks, cassette tapes and CDs for music, videos and files. Portable storage options are more efficient these days, giving users the flexibility to choose between such options as USB flash drives, SD memory cards and microSD cards, and solid-state drives (SSDs) for their data storage needs.

But with so many available options, it can be tough to determine what storage type is right for the situation.

The Basics: Main Traits

If each storage option were to be described in two words, one might use portable convenience for SD memory cards; flexible usage for USB flash drives; and highest performance for SSDs.

As a removable storage option, USB flash drives are versatile and inexpensive, and generally durable. Most operating systems read and recognize this device as soon as it is plugged in, making it easy to use with mainly desktop and portable computing devices. While they are good for moving files, storage capacity can be limited. They are not ideal for usage with write-intensive applications.

SD and microSD memory cards are another easily portable and removable storage device that ranges from small to massive capacity levels. The cards can support a wide array of data, from 4K video to mobile apps, on the smallest form factor. They fit into a variety of devices, including smartphones, cameras, drones, automobiles and computers. The additional storage they provide can free up internal memory and boost a device’s speed when users attempt to store and access data, music and videos. The simple portability of the SD memory cards allows easy share/transfer of user data among billions of various SD-supported devices in the market.

SSDs are not removable storage and are typically built into larger devices like computers and servers. They use non-volatile flash memory, making it fast to access files from one. SSDs can come in a variety of storage sizes, including 16 GB, 32 GB and 64 GB, but because they are used mainly for larger applications such as a system backup device, most portable SSDs’ capacity start at 128 GB.

Differentiating Factors & Similarities

The two main factors that distinguish the three options from each other are ecosystem and application.

The majority of the content created for microSD/SD memory cards is from many types of cameras or mobile devices, both of which benefits from these cards’ small form factor. A USB flash drive is more of a content carrier than something one uses for content creation; therefore, it does not need to be as small in physical size as an SD memory card. An SSD’s ecosystem is often in enterprise storage and database applications, meaning it does not need to be removable, but does require higher performance and capacity.

They are similar in that they are all flash-based products, requiring a controller and NAND flash. Additionally, if a user has a bridge IC/adapter, a user can make the individual product into a different type of storage.

For example, some companies sell a microSD memory card bundle with a card reader, that lets people use a card as a USB flash drive. Other companies sell a portable SSD that has a SATA SSD + USB adapter. These variations allow each of the storage options to easily convert to a different kind of usage.

Use Cases and Applications

On the industrial side, compared with old hard disk drives, all three storage choices can function as a boot drive to improve a device’s boot-up time. The trend leans toward SSD as the preference, though some designs use USB flash drives and SD memory cards.

For consumers, an SSD is mainly a system device used as a main storage option in their computer. USB flash drives are mainly a content/file carrier or transfer mechanism when there is no Wi-Fi or Internet connection, since the USB can facilitate the transfer between computers easily. Unlike microSD memory cards, there are transfer limitations, because cameras and phones do not have USB slots.

SD and microSD memory cards are often used to record and store photos, music, videos, apps and files. Both card types can store data taken directly from a device while users are on the go, such as photos on a vacation or videos from a child’s birthday party, increasing their value because they allow users to store their memories as they occur.

Because SSD capacity is substantially larger than SD or USB flash drives, data center applications often use them for cached data. However, industrial applications also use USB flash drives for file transfers (even alongside SSD), and often use SD memory cards because of the versatility of storage sizes (with coming prototypes going up to 1 TB) and their portability.

Choosing the Best Option Based on Needs

To choose the best removable storage option for their needs, users must understand and determine the device needs first, as different devices require different storage options.

Most video and still cameras, dash-cams, drones, Android smartphones and action cameras use microSD or SD memory cards for storage and file transfer. Some laptops have SD memory card slots, but many others only offer a USB for file transfer. Because an SSD is not a removable device, most options to add storage are aftermarket and require more advanced computer knowledge to use them, whereas USB flash drives and SD memory cards offer plug-and-play convenience, making them user-friendly.

It is rare that a consumer would use or change an SSD. One instance might be if a consumer’s laptop had an issue with storage and the consumer needed to buy an SSD to replace the built-in storage option, or to upgrade it. Normally, the average consumer would not want to purchase an SSD as a storage device unless he or she was a do-it-yourself computer builder, whereas anyone can use removable storage devices like USB flash drives and SD memory cards.

For industrial-grade users, it’s important to know the protocol requirements (including interface type – e.g., USB/SD/SATA/SAS/PCIe) for their application, as well as the capacity requirement and the form factor the application needs, before deciding what type of storage to use.

Ask the Right Questions

To determine the right storage option, users should ask themselves:

  • What does my device need?
  • How much do I want to spend?
  • Do I need the storage device to be removable?
  • Do I need the storage device to be portable?
  • What application am I using the storage device for?
  • What are my application’s capacity and file transfer speed requirements?
  • What kind of tech knowledge do I need to use the storage device?

With such a variety of storage device types, from SSD, USB flash drives, SD and microSD memory cards – and the many choices within each of those categories – consumers and industrial users alike have a multitude of options for their storage needs, no matter what the situation. By asking the right questions, users can feel confident they are selecting the best device for their needs every time.

Keith Tsai is strategic account manager at Phison Electronics Corp. Tsai can be reached at keith_tsai@phison.com.

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