HDD vs eMMC vs SSD – How to choose and compare computer storage?

A number of electronic devices such as computers, laptops use and need storage. When buying a laptop or a desktop, you’ll probably stumble on HDD vs eMMC vs SSD comparison. These are types of storages you might see as part of storage technical specification. SSD stands for Solid State Drive, HDD stands for Hard Disk Drive and eMMC stands for Embedded Multi-media card. In this article, we provide basic information to help you choose and compare various storage technologies. All storage technologies have the same fundamental purpose of storing data, but they work very differently and have different characteristics.

While most users may know the distinction, it is important to understand that storage is not the same as memory. If you want to learn more about memory, you may review this article.

What is a HDD (Hard Disk Drive)?

HDDs are the traditional storage devices that have been around pretty much since the personal computers came to existence. They help permanently store and retrieve data using spinning disks (platters). It also uses a tiny moving read and write heads attached to the end of an arm, that moves over the spinning disk to perform the read write operations. These platters have a magnetic coating and spin at high speeds. Each platter’s surface is organized into concentric circles called tracks and subdivided into sectors, which help the drive locate data faster. Bottom line, HDD uses both electricity and magnetism to store and retrieve data.

This technology has worked very well for many applications and for decades. Research and innovation in the storage industry has produced better technologies suited for some of the applications.

What is an eMMC?

eMMC stands for “Embedded Multi Media Card.” It is a type of non-volatile (fancy way of saying permanent!) memory storage commonly used in embedded systems. The term ’embedded’ comes from the fact that manufacturers usually solder them onto other circuit boards, making them specialized for a specific electronic device or computer.

eMMCs use the same underlying technology as MMCs (MultiMediaCards), which are removable. Subsequently SD cards over took MMCs which were used for applications such as digital cameras, etc. Manufacturers designed them for use in mobile devices, tablets, and budget laptops. At the time of this writing, they can reach transfer rates up to 400MB/sec. 

eMMCs use something called a NAND flash memory that contains a collection of memory cells to hold the data as a set of 1s and 0s. It also has a controller to perform the operation of read and write. Thus, unlike HDDs, these devices use electricity—with no moving parts—to transfer and store data.

What is SSD?

A solid-state drive(SSD), is also a non-volatile, persistent data storage that uses flash memory with no moving parts, very similar to eMMC. SSDs provide faster load times and silent operation (because they don’t have moving parts like HDD), thus resulting in better durability and reliability. If eMMC is cheaper, why should we use SSD? Well, the reason is that designers generally build them to transfer more data within the same time period. So, SSDs are also generally larger in size for the same storage size, everything else being equal.

Most newer SSDs may also support newer and better storage protocols like NVMe (Non-volatile memory express). Consequently, they allow for lightning-fast transfer speeds up to 7.0GB/s at the time of this writing.

Interfaces SATA vs NVMe

You may have seen these abbreviations used along with storage devices for computer specs. Think of them as a channel or protocol that SSDs or HDDs use to communicate with the rest of the computer(or motherboard). If you are a hardware enthusiast trying to put together a computer by sourcing your own parts, then you might want to continue reading this section. But if you are just trying to understand the basics and purchase a laptop/computer, then you may skip the rest of this section.

SATA

SATA stands for Serial Advanced Technology Attachment. It came into existence at around year 2000 and the next 10-15 years, SATA was the single largest interface or connector to connect a hard drive to a motherboard. HDDs and SSDs need the SATA cable to connect to the motherboard. These cables implement the interface with various SATA versions such as SATA I, SATA II & SATA III. If you used our tool, PriceWired to compare laptops, then you might have noticed the technical specifications for storage.

NVMe

Simply put, NVMe is almost always better and faster than SATA interface. When SSDs started showing up in the market, SATA was still the primary interface. Subsequently, the SSDs were hitting the SATA transfer rate limit of 500 MBps. It was time for SSDs to seek another partner! Enter NVMe. In 2011, the industry introduced Non-Volatile Memory Express (NVMe) technology, which allowed SSDs to surpass the speed limitations of SATA. NVMe uses PCIe (Peripheral Component Interconnect Express) protocol. At the time of this writing, NVMe is has hit speeds of 7GBps. With NVMe, SSDs can talk to CPU directly which was not possible before and opened more opportunities for advancements in speed and performance.

Form Factors

Form factor refers to physical size and shape of a hardware device. You don’t need to worry about this section if you are not going to open up your computer or attempting to replace your storage device but it helps to understand what it means.

The most common form factors for HDD are 2.5 inch and 3.5 inch. eMMC devices are soldered on the motherboard directly, so the common form factors are quite small ranging from 11mm to 12mm for width and 13 mm to 18mm of length.

SSDs are slightly different – the form factors for SSDs uses numbers and/or names. They are 2.5 inch, mSATA, U.2 and M.2. mSATA stands for mini SATA which is much smaller than SATA at about 1.18″ x 2″. U.2 also uses 2.5 inch size. M.2s are usually around 22mm to 80mm.

HDD vs eMMC vs SSD

Now for the topic we have all been waiting for! Without getting into too many technical details, here is a high-level comparison of HDD vs eMMC vs SSD? Below table should help you get there!

Conclusion

We tried to provide enough information to get most of you going with your purchase decision or just preliminary research however, if you are a more advanced reader and wants to know a bit more detail, we highly recommend this video

Computer storage is one of the key technical specifications. HDDs have come a long way and still have their place in the industry. HDDs should be used for applications such as backups where there is a need for very large size, potentially not a lot of concern for noise and cost efficiency is important.

eMMCs may fit a very specific need where you need very small form factor soldered into a circuit board but need the speed and efficiency for an additional cost. Budget laptops are good candidates for eMMCs.

SSDs on the other hand have become the most popular but they do come with a cost. Whatever electronic device you are considering, if you don’t mind the cost, we highly recommend going the SSD route.