A Simple SSD Comparison to HDD

In This Corner: The Hard Disk Drive (HDD)

The traditional spinning hard drive has been a standard for many generations of personal computers. Constantly improving technology has enabled hard drive makers to pack more storage capacity than ever, at a cost per gigabyte that still makes hard drives the best bang for the buck.

ibm ramacAs sophisticated as they’ve become, hard drives have been around since 1956. The ones back then were two feet across and could store only a few megabytes of information, but technology has improved to the point where you can cram 10 terabytes into something about the same size as a kitchen sponge.

Inside a hard drive is something that looks more than a bit like an old record player: There’s a platter, or stacked platters, which spin around a central axis — a spindle — typically at about 5,400 to 7,200 revolutions per minute. Some hard drives built for performance work faster.

hard drive diagramInformation is written to and read from the drive by changing the magnetic fields on those spinning platters using an armature called a read-write head. Visually, it looks a bit like the arm of a record player, but instead of being equipped with a needle that runs in a physical groove on the record, the read-write head hovers slightly above the physical surface of the disk.

The two most common form factors for hard drives are 2.5-inch, common for laptops, and 3.5-inch, common for desktop machines. The size is standardized, which makes for easier repair and replacement when things go wrong.

The vast majority of drives in use today connect through a standard interface called Serial ATA (or SATA). Specialized storage systems sometimes use Serial Attached SCSI (SAS), Fibre Channel, or other exotic interfaces designed for special purposes.

Hard Disk Drives Cost Advantage

Proven technology that’s been in use for decades makes hard disk drives cheap — much cheaper, per gigabyte than solid state drives. HDD storage can run as low as three cents per gigabyte. You don’t spend a lot but you get lots of space. HDD makers continue to improve storage capacity while keeping costs low, so HDDs remain the choice of anyone looking for a lot of storage without spending a lot of money.

The downside is that HDDs can be power-hungry, generate noise, produce heat, and don’t work nearly as fast as SSDs. Perhaps the biggest difference is that HDDs, with all their similarities to record players, are ultimately mechanical devices. Over time, mechanical devices will wear out. It’s not a question of if, it’s a question of when. HDD technology isn’t standing still, and price per unit stored has decreased dramatically.

HDD manufacturers have made dramatic advances in technology to keep storing more and more information on HD platters — referred to as areal density. As HDD manufacturers try to outdo each other, consumers have benefited from larger and larger drive sizes. One technique is to replace the air in drives with helium, which reduces reduces friction and supports greater areal density. Another technology that should be available soon uses heat-assisted magnetic recording (HAMR). HAMR records magnetically using laser-thermal assistance that ultimately could lead to a 20 terabyte drive by 2019.

The continued competition and race to put more and more storage in the same familiar 3.5” HDD form factor means that it will be a relatively small, very high capacity choice for storage for many years to come.

HHD and SSD Comparison showing the inside of a hard drive

In the Opposite Corner: The Solid State Drive (SSD)

Solid State Drives (SSDs) have become much more common in recent years. They’re standard issue across Apple’s laptop line, for example the MacBook, MacBook Pro and MacBook Air all come standard with SSDs. So does the Mac Pro.

ssd hard drive inside opened upSolid state is industry shorthand for an integrated circuit, and that’s the key difference between an SSD and a HDD: there are no moving parts inside an SSD. Rather than using disks, motors and read/write heads, SSDs use flash memory instead — that is, computer chips that retain their information even when the power is turned off.

SSDs work in principle the same way the storage on your smartphone or tablet works. But the SSDs you find in today’s Macs and PCs work faster than the storage in your mobile device.

The mechanical nature of HDDs limits their overall performance. Hard drive makers work tirelessly to improve data transfer speeds and reduce latency and idle time, but there’s a finite amount they can do. SSDs provide a huge performance advantage over hard drives — they’re faster to start up, faster to shut down, and faster to transfer data.

Benefits of a SSD Hard Drive

SSDs can be made smaller and use less power than hard drives. They also don’t make noise, and can be more reliable because they’re not mechanical. As a result, computers designed to use SSDs can be smaller, thinner, lighter and last much longer on a single battery charge than computers that use hard drives.

Many SSD makers produce SSD mechanisms that are designed to be plug-and-play drop-in replacements for 2.5-inch and 3.5-inch hard disk drives because there are millions of existing computers (and many new computers still made with hard drives) that can benefit from the change. They’re equipped with the same SATA interface and power connector you might find on a hard drive.

Planning for the Future of Storage

If you’re still using a computer with a SATA hard drive, you can see a huge performance increase by switching to an SSD. What’s more, the cost of SSDs has dropped dramatically over the course of the past couple of years, so it’s less expensive than ever to do this sort of upgrade.

Whether you’re using a HDD or an SSD, a good backup plan is essential because eventually any drive will fail. You should have a local backup combined with secure cloud-based backup like Backblaze, which satisfies the 3-2-1 backup strategy. To help get started, make sure to check out our Backup Guide.

Hopefully, we’ve given you some insight about HDDs and SSDs. And as always, we encourage your questions and comments, so fire away!

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