Hard Drive Explainer - HDD vs SSD vs M.2 drives


A slow internal hard drive is often the culprit of a PC that feels like molasses. So before you toss your aging PC into the trash, upgrading the storage drive on your laptop or desktop is perhaps one of the easiest and most cost-effective things you can do to alleviate some of the speed bottlenecks.

This is especially true of laptops with older mechanical storage, like hard disk drives, which are limited by how fast the platters can spin. Though you can cheaply upgrade to a faster hard disk drive, or HDD, with faster revolutions per minute (RPM), like a 7200 RPM HDD, you’re better off switching to a solid-state drive. Unlike HDDs, SSDs don’t have spinning platters, so your processor can quickly read from and write to the drive. Another benefit of going with an SSD is that since there are no moving mechanical parts, these drives will be less prone to failure. This is especially important if you’re using a laptop that gets bumped and knocked around or if you’re working in the field where more hostile environments -- including dust, dirt, and extreme temperatures -- can do damage to an HDD.

What type of SSD should I buy?

Now that you’ve settled on upgrading your internal drive to a solid-state drive -- do note that some laptops, like the drives on Apple’s MacBook Air and MacBook Pro, cannot be easily upgraded, so you’ll need to anticipate what storage capacity you think you’ll need over the lifespan of these notebooks at the time of purchase -- you’ll need to figure out what SSD will fit your system.

In general, if you’re upgrading from an HDD, you’ll need a SATA drive. These drives come in the same 2.5-inch form factor as many of the disk drives on a laptop, and you’ll just need to unscrew the existing hard drive and swap in the SATA-based SSD.

More modern laptops that already ship with solid-state drives will usually support the newer and more compact M.2 format, which resembles a big stick of chewing gum. In this case, you’re likely upgrading your M.2 SSD because you either need faster speeds, more storage capacity, or a combination of both. Unlike HDDs, where speed is measured in RPM, SSDs are benchmarked for their reading speeds and writing speeds, both measured in MB-per-second, or MB/s or MBps. SATA SSDs average around 500 MBps. Crucial’s highly rated MX500 SATA III SSD is priced at just $114.99, making it an affordable purchase for 1TB of storage.

M.2 drives come in two varieties: NVMe and non-NVMe formats. NVMe is the preferred standard if your system supports it. This format was developed by a consortium of manufacturers including Samsung, Dell, Seagate, and SanDisk (now part of Western Digital). The format is fast and comes with very low latency, as it connects directly to your motherboard rather than a SATA interface. On a lot of systems, NVMe M.2 drives read and write data four times as fast as standard SATA SSDs, which are already a lot speedier than their mechanical HDD counterparts.

Additionally, there are a variety of factors that affect NVMe SSD performance. Those with a need for speed will want to choose an x4 PCIe NVMe drive over an x2 PCIe drive, and NANDs made up of single-level cell (SLC) drives are still faster than multi-level cell (MLC), triple-level cell (TLC), and others.

And because desktops aren’t as space-constrained as laptops, you’ll find some systems, like larger workstations and gaming rigs, will often support more than one drive. These systems can also support a combination of drives, allowing you to augment your storage between multiple SATA SSDs, NVMe M.2 drives, and even larger drives that occupy one of the PCIe x4 or PCIe x16 slots, like SanDisk’s 4TB PCIe Gen 3 drive. If you're building a PC with multiple SSDs, consider putting the operating system on the drive with the fastest read and write speeds and choosing a less expensive SSD format -- like SATA drives -- for storing large files.

How big of a storage drive do I need?

Because of their design, NVMe uses a portion of their available NAND as primary and secondary storage, so you’ll want to buy a drive with enough capacity to handle caching duties. If a drive gets to about 80% or more full, the SSD’s performance will be affected, so a rule of thumb is you’ll want to buy a drive with twice as much capacity as you think you’ll need. If you anticipate 1TB of data storage will be required, it may be a safe bet to get a 2TB. This way, you’ll not only have room to grow, but your system will have plenty of cache space.

Most systems today ship with a base 120GB solid-state drive, and the smaller size makes these drives more affordable. However, if you find yourself storing lots of files, photos, videos, or even games and apps, you’ll want to upgrade to a larger capacity drive. Premium laptops these days ship with SSDs in the 500GB range, though you can upgrade to a 1TB or 2TB capacity. A new computer with a drive size between 500GB and 1TB is ideal for most uses. If you’re upgrading to a larger capacity drive, Samsung’s 970 EVO is just $139.99, while the 500GB edition of the same drive starts at $69.99. 

There are even larger capacities, extending to 4TB and beyond, but, in general, these drives are way too costly for most consumers, and resorting to external storage for your files can help cut costs. Alternatively, you can also add an external SSD or network-attached storage (NAS), like a My Cloud drive, if you find yourself short on space.

Are hard disc drives obsolete?

The standard hard disc drives are definitely not obsolete because they provide the most value when you’re storing large files. Spinning platters are still the preferred storage medium for data centers, cloud storage facilities, and servers.

On desktops and some mobile workstations, you can equip your system with two types of drives to help keep costs low. Gamers will often keep the main operating system -- Windows, in this case -- and all the important apps on the SSD while keeping files that don’t get used often on the HDD. If you have the option to configure a PC with dual drives, you can choose a smaller capacity SSD and pair it with a larger capacity HDD to help balance speed, price, and performance. 

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