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HDD or SSD? How to Buy Hard Disk Storage Now

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(Updated for 2018) Should you go with HDD or SSD for your data storage? Solid-state drives and hard disk drives come in all different shapes, colors, and sizes, so when it comes to selecting the right hard disk storage, business customers should understand the scope and purpose of the different types of hard drives that are available to them.

Differentiating hard disk drives (HDD) from solid-state drives (SSD)

Choosing whether to buy a HDD or SSD is the first and most important choice. Both fulfill the same function but are mechanically very different and have unique pros and cons.

For those who are unfamiliar, an SSD is a type of drive that stores data in flash memory cells. Unlike a HDD, with its spinning magnetic platters and actuator arm, SSDs have no moving parts. It is the same as the memory inside USB thumb drives.

SSDs have a performance advantage over spinning disks that is noticeable to the end user—faster boot times and a “snappier” feel when using production applications. Since there are no moving parts, SSDs consume less power and tend to be more reliable. SSDs also operate in silence.

Performance comes at a cost, however. Solid-state drives are generally five or six times more expensive per gigabyte of storage than their spinning counterparts.

HDD vs SSD cost

Determining whether a HDD or SSD fits your needs is a question of performance and capacity.

  • How much data do you need to support now? What about in the coming years?
  • What kind of benefit will your business experience from added performance?
  • What is your budget for data storage?

HDD vs SSD ven

Hybrid data storage is becoming quite common for businesses of all sizes.

In a workstation PC, you might see both SSD and HDD storage. The operating system and production applications are typically loaded on the SSD, from which the system boots. A HDD stores files and lesser-used applications. Seagate hybrid drives house both SSD and HDD in a single chassis.

Companies might apply a similar setup at the server level. Hard drives are typically used in backup archives and shared storage servers. Performance-optimized application servers often use solid-state drives.

Hard Drive Form Factors

Internal vs. External Drives

Both HDD and SSD are designed to either fit inside a computer system, or as a portable standalone device. Inside, the respective drives work in essentially the same manner.

Internal Hard Drive Form Factors

  • 3.5-inch drives are designed for desktop systems, servers, and rack enclosures. It is exclusive to HDD. These drives can have a higher capacity and are usually the most cost efficient storage options available.
  • 2.5-inch drives (called “mobile” drives, though designed for internal use) are designed for laptop systems. They usually have smaller capacities and are slightly more expensive per-gigabyte, but offer better performance according to manufacturer specs.

You can put a 2.5-inch drive inside a desktop computer case with the help of a mounting bracket. Velcro also works in a pinch.


External Drive Form Factors

  • Desktop external hard drives contain one or two 3.5-inch HDDs in a hard plastic or metal enclosure. They have large capacities (4-8 TB) and are usually used for mobile backup and storage.
  • Wireless attached storage drives can be accessed over a Wi-Fi by other computers on the network. It is usually used for streaming media, and has capacity between 500 GB and 2 TB. It can be either a 3.5- or 2.5-inch encased drive.
  • Portable external hard drives have sleeker designs than their bulkier desktop counterparts, and are meant for easy transport. They can be either 2.5-inch HDD or SSD, and range in capacity from 32 GB to 6 TB.

data locker hdd


Portable hard drives can have extra features like encryption and a ruggedized build, like this Data Locker Enterprise portable hard drive meant for use in the field.







  • SATA III is the current interface found on internal drives used by small- and medium-business users. SATA III controllers are designed for inexpensive performance. If you have an older system with SATA II or SATA ports, SATA III is backwards compatible.
  • SAS is an interface found on HDDs designated for use in large enterprise storage arrays. SAS drives are designed for multiple users accessing data simultaneously, and added error protection features.

New Technology—M.2 and NVMe SSDs


Mainstream SSDs predominantly use the SATA III interface but there is new technology that the enterprise realm has begun to adopt for solid state drives. Special M.2 and NVMe drives plug solid state storage directly into faster slots on a motherboard—M.2 or PCI-e. This allows for even faster data transfers and performance, which are capped at 6 Gb/s by the SATA III interface.

External Hard Drive Interfaces

  • USB 3.0 is the predominant interface for computers made after 2012. The vast majority of available external hard drives connect via USB 3.0 interface. If you have an older system with USB 2.0 ports, don’t worry—USB 3.0 is backwards compatible. You will not experience the faster data transference offered by USB 3.0, however.

thunder bolt & usb

  • Thunderbolt (shown above) is an Apple and Intel interface technology that combines PCI Express (a fast slot on the motherboard) and DisplayPort into a single connection. It allows for the daisy chaining together of storage devices, monitors and other peripherals to a single system.

Gauging Hard Disk Performance

What does it mean to have a “fast” hard drive? Performance is measured differently in HDDs and SSDs. Here are the terms to know for when talking about speed.

Use RPM for Hard Disk Drives

The faster the disk inside the hard drive spins, the faster you can transfer data to and from the drive.

  • 5,400 RPM – Standard drive speed for large-capacity archive hard drives designed for backup purposes and cold storage.
  • 7,200 RPM – Standard drive speed for the main HDD on a modern PC designed for day-to-day production use, and in network attached storage (NAS) devices.
  • 10,000 – 15,000 RPM – Standard drive speed for enterprise storage arrays. These hard drives usually have SAS interfaces.

One other metric deserving of attention:

  • Cache – A special section of memory on the drive that helps move blocks of data around the disk. The larger the capacity of cache, the better the HDD responds. Modern drives have 8-128 MB of cache memory.

Use Read/Write Speeds for Solid State Drives

SSDs are benchmarked for data transference by the number of megabytes per second it reads and writes data. Manufacturers quantify this metric—called sequential read and write speeds—and many post on the drive’s packaging or manual. Independent benchmarks seek to confirm these speeds.

Understand that, as with any benchmarking, system variables come into play, as does the nature of the data being transferred.

Different types of NAND cells, which comprise the insides of solid state drives, have different data transference speeds and architectures. There are several NAND types used in modern drives.

  • Multi-Layer Cell (MLC) – Low cost, fastest read/write times, high endurance.
  • Triple-Layer Cell (TLC) – Lowest cost, slightly slower read/writes compared with MLC, lower durability ratings.
  • 3D V-NAND – Technology exclusive to Samsung SSDs that uses vertically stacked NAND cells. Increased storage capacity at a lower price, though slightly slower than MLC.

What is more durable: HDD or SSD?

Both HDDs and SSDs wear out over time and eventually fail. Whether that happens in six months or six years, you never really know until the signs of hard drive failure are upon you. A company should always have critical data backed up and replacement drives in stock. Think of data storage hardware as a commodity.

With HDDs and SSDs, drive wear happens differently. HDDs and their spinning platters and mechanical arms can succumb to physical shock, or simply wear out over time. In recent years, cloud storage provider BackBlaze released data about which hard drive brands are the most reliable in their datacenter, but these methods were met with controversy in the storage community.

Even though SSDs have no movable (breakable) parts, they have a finite a lifetime because the NAND degrades after a certain number of program/erase (P/E) cycles. SSDs are typically rated for 4,000-5,000 P/E cycles, but this is just an average estimate.  In general, SSD technology is very reliable and drives will most likely reach obsolescence before failure.

Related content: 7 Tips to Maximize SSD Endurance

Special types of Hard Drives

Enterprise Drives – Enterprise HDDs and enterprise SSDs are built for datacenter use. Manufacturers design these types of drives for 24/7/365 use in servers or workstations.

hdd ssd enterprise chart

Helium HDDs – HGST Ultrastar He-series drives have the spinning data platters housed in a helium-filled chamber. The idea is that since helium is lighter than air, the mechanical parts experience less friction, thus reducing wear and tear on the drive.

NAS HDDs – Even though virtually all HDDs work with network attached storage, some drives like the WD Red series are optimized for NAS systems. Like enterprise drives, they are tested for 24/7 operability, have vibration-resistant features, and have firmware that helps with compatibility and integration.

Surveillance HDDs  – The WD Purple series has firmware to support multiple video surveillance cameras as part of a multi-bay surveillance solution. They are tested for 24/7 operation and are a standard 3.5-inch / SATA III form factor and interface.


Deciding on data storage hardware comes down to performance needs and budget. Whether you choose HDD or SSD—or go with a hybrid setup—make sure to understand the variants of each method of hard disk storage.

HDD or SSD? How to Buy Hard Disk Storage Now
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HDD or SSD? How to Buy Hard Disk Storage Now
Should you go with HDD or SSD for your data storage? Solid-state drives and hard disk drives come in all different shapes, colors, and sizes, so when it comes to selecting the right hard disk storage, business customers should understand the scope and purpose of the different types of hard drives that are available to them.
Adam Lovinus

Adam Lovinus

A tech writer and Raspberry Pi enthusiast from Orange County, California.

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