Is hard disk important in a computer?

A hard disk drive (HDD) is a key component of modern computers. It provides long-term storage for the operating system, applications, and data. With PCs and laptops, the hard drive is usually installed internally, while external hard drives are common for additional storage and backups. But are hard disks still necessary in the age of solid state drives and cloud storage? Let’s take a closer look at the role of the hard disk.

What is a hard disk?

A hard disk drive contains one or more rigid platters coated with magnetic material. These platters spin rapidly while a movable arm with read/write heads hovers above the surface to access data. Because hard disks rely on mechanical parts, they are susceptible to damage from shocks and vibration. However, modern drives include features like ramp loading to park the heads safely when powered off. The key components of a hard drive are:

  • Platters – Made of non-magnetic material like aluminum or glass and coated with a thin layer of magnetic material.
  • Read/write heads – Located at the end of the actuator arm, these heads float just above the platter surface on a thin cushion of air.
  • Spindle – A motor rotates the platters at speeds up to 15,000 RPM in consumer drives.
  • Actuator arm – Driven by the voice coil, this component moves the heads across the platters.
  • Firmware – Low-level software that handles operations like motor control, data reads/writes, and caching.

Hard drives store data by magnetizing tiny regions of the platter in a certain polarity to represent 1s and 0s. The servo sectors positioned around the platters allow the actuator arm to accurately locate tracks and sectors for data access. An HDD controller coordinates the components and interfaces with the computer.

Brief history of hard drives

IBM introduced the first hard drive in 1956 with the 305 RAMAC system. It could store a whopping 5 MB on fifty 24-inch platters! By the early 1980s, capacities reached 10-40MB on drives used in the original IBM PC. Other important developments include:

  • 1970s – Winchester drives sealed the platters in a dust-free enclosure.
  • 1979 – Thin film heads replaced ferrite heads for better storage density.
  • 1980s – MR heads enabled further density improvements.
  • 1990s – PRML and EPRML signal processing increased areal density.
  • 2000s – Perpendicular recording allowed densities over 100 Gb/in2.
  • 2010s – SMR, He, shingled heads pushed densities over 1 Tb/in2.

Today, consumer hard drives provide anywhere from 500GB to 16TB capacities from just a few platters. Data centers employ HDDs up to 20TB for economical bulk storage. Maximum areal densities have exceeded 2.4 Tb/in2 demonstrating there is still room for growth.

Advantages of hard disks

Hard disk drives became the dominant form of computer storage for several key reasons:

  • High capacity – HDDs are capable of storing vast amounts of data economically. This makes them suitable for bulk storage needs.
  • Speed – Although not as fast as SSDs, HDDs can sustain sequential reads/writes over 100 MB/s. Data transfer speeds continue to improve with faster spinning platters, better caching, anddual actuator arms in some enterprise drives.
  • Low cost per GB – The mechanical nature of hard drives means they offer more affordable storage than flash-based SSDs. HDD capacity grows at a lower cost than SSDs.
  • Nonvolatile storage – Data persists on HDDs even when powered off. This contrasts with volatile RAM that needs constant power.
  • Mature technology – Mass production over decades has refined HDD technology. Manufacturers continue to develop new innovations as well.

These strengths have maintained hard disks as an essential component in computers despite new storage tech.

Use cases

Some typical applications that leverage the advantages of HDDs include:

  • Desktop/laptop PCs – Operating systems, programs, and files rely on hard drives for primary storage.
  • Game consoles – The large games and media files require substantial inexpensive storage.
  • VR headsets – 360° video captures demand high-capacity drives.
  • Data centers – Servers stack 10TB+ HDDs in vast arrays for affordable online storage.
  • Network attached storage (NAS) – RAID HDDs provide shared storage that is more scalable than SSDs.
  • Surveillance systems – Dozens of camera feeds require efficiently storing tremendous footage.
  • Bulk cold storage – Archives, medical imaging, research data, etc. still go on hard disks.

HDDs are well-suited for read-intensive workloads that stream large files. Use cases that are write-heavy or require quicker access times may benefit from SSDs. However, HDDs can supplement flash in tiered storage environments.

Importance in PCs

Hard drives remain a vital component in today’s computers. Here are some reasons why:

  • Operating systems are optimized for HDDs and expect them to be present.
  • Booting from SSDs provides a faster initial experience. But HDDs store the bulk of apps and files.
  • HDD capacities and price points accommodate large games, media libraries, creative content.
  • Most consumer SSD capacities remain in the 512GB-2TB range. HDDs offer up to ~16TB.
  • Replacing or upgrading hard drives is straightforward for more storage.
  • External portable HDDs conveniently add storage and enable backups.
  • Newer interfaces like SATA Express and PCIe maintain HDD relevance.

SSDs provide benefits like faster boot times, quicker game loads, and overall snappiness. However, HDDs deliver substantial storage capacity at an affordable cost per gigabyte. The typical PC configuration combines a smaller SSD paired with a higher-capacity HDD.

Reliability

Early hard drives were prone to failures and had limited lifespans. But modern drives have become remarkably dependable through improvements like:

  • Stable data heads and touch down ramps to avoid platter contact.
  • Sealed enclosures to reduce particulate contamination.
  • Error correction codes to recover from defects.
  • Contact start stop to avoid wear from spinning up.
  • Predicted failures from SMART diagnostics to warn of problems.
  • Helium filling to reduce turbulence and stresses.

Manufacturers rate newest HDDs for 2.5 million hours MTBF and 550TB per year workloads. Enterprise drives meant for 24/7 operation are rated up to 2.8 million hour MTBF. Real world lifespans comfortably exceed warranties that cover 3-5 years. Proper ventilation, cooling, and vibration dampening also promote longevity.

While HDDs are still electro-mechanical devices subject to eventual failure, their dependability has proven more than adequate for most applications. Redundant drives, backups, and RAID provide additional data protection where needed.

Speed and performance

Hard drive speeds lag far behind SSDs, but there are a few metrics that measure HDD performance:

  • Rotational speed – Faster RPMs yield higher sustained transfer rates but consume more power. Common speeds are 5400 RPM (laptops), 7200 RPM (desktops), 10,000-15,000 RPM (enterprise).
  • Average seek time – Time needed to move heads to a random track. Around 8-10 ms for consumer drives.
  • Interface – SATA interfaces up to SATA III (6Gbps) are most common. Enterprise uses SAS, Fibre Channel.
  • Buffer size – Larger buffers improve burst speeds. 16-256 MB caches help smooth transfers.
  • Areal density – More bits per square inch provides greater capacity and sequential speed.

Peak transfer rates can surpass 200MB/s with high RPM, although sustained speeds are lower. Seek times are still in the millisecond range. Enabling caching, native command queuing, and aligning partitions can help optimize real-world HDD performance.

HDD vs SSD Speed Comparison

Hard Disk Drive (HDD) Solid State Drive (SSD)
Peak sequential read speed Up to 210 MB/s Over 3 GB/s
Peak sequential write Up to 210 MB/s Over 3 GB/s
Random read speed IOPS Below 200 IOPS Over 100,000 IOPS
Random write IOPS Below 200 IOPS Over 100,000 IOPS
Latency 8-10 ms average 0.1 ms or less

This shows SSDs outclass HDDs on all speed metrics, particularly random IOPS. Still, hard drives can deliver acceptable overall performance thanks to features like caching. Upgrading to an SSD provides a significant speed boost for key workloads.

Noise and power

Some downsides of HDD technology originate from the moving platters and heads. Spinning disks and mechanical seeks generate audible noise compared to silent SSDs. Their motion also requires more power:

  • 3.5-inch desktop drives – Around 6-9 Watts while active.
  • 2.5-inch notebook drives – Roughly 2-3 Watts when active.
  • SSDs – Typically under 1 Watt active power.

Newer drives with technologies like ramp unloading can “park” the heads when not in use to reduce power consumption and noise. Smaller form factors naturally use less energy as well. But in general, HDDs require more electricity than SSDs.

Shock and vibration resistance

Dropping a hard drive or excessive vibration remains a risk due to internal moving components. The heads could impact the platters during a sharp jolt, scratching the surfaces. HDDs contain acceleration sensors to detect freefall and quickly park the arms. However, spends disks are still vulnerable to misalignment or scratched surfaces if impacted during operation.

By contrast, SSDs have no moving parts and can withstand much stronger shocks without harm. Modern laptops and external drives with HDDs contain extra shock protection inside, but their mechanics are intrinsically more delicate than solid state storage. Enterprise HDDs designed for datacenter racks feature vibration dampening technologies to ensure reliable 24/7 operation.

Long-term reliability

Although today’s HDDs are robust for most consumer workloads, their mechanical nature means they’re bound to wear out eventually. The primary limitations are:

  • Disk platter coatings wear from head contact during reads and writes.
  • Motors have a finite lifespan before breakdown.
  • Bearings can degrade over time, especially in hot environments.
  • Heads risk crashing into platters at high speeds.

Evidence of this finite lifespan shows up in the failure rate curves for HDDs. Annualized failure rates start below 1% but slowly increase after 2-3 years of service. Enterprise drives rated for higher duty cycles exhibit this behavior faster.

SSDs do not have moving parts subject to mechanical wear. However, NAND flash memory has limitations on erase cycles before cells wear out. High-quality SSDs are rated for thousands of program-erase cycles to attain 5+ year lifespans. This gives SSDs an intrinsic long-term reliability advantage over HDDs.

Magnetic storage challenges

While HDD technology has progressed remarkably, it faces physical barriers from magnetic storage:

  • Superparamagnetic limit – Materials lose magnetism below certain sizes, stalling areal density gains.
  • RAM limits – The head actuator arm is nearing the limits of fast repositioning.
  • Write delays – Magnetically aligning bits takes nanoseconds, slowing writes compared to SSDs.
  • Platter bends – Spinning disks bend slightly, affecting data density limits.
  • Shingled writing – Overlapped tracks sacrifice rewrite ability for more capacity per platter.

SSDs based on flash memory sidestep these magnetic issues altogether. However, HDD engineers continue finding ingenious ways to push magnetic storage forward. Bit-patterned media, HAMR, MAMR, and energy-assisted technologies aim to sustain progress for more years. But eventually magnetic storage will hit impassible limits.

Future SSD competition

Solid state drives exceed hard disks on performance and resilience. As SSD pricing falls, HDDs lose dominance in more applications:

  • NVMe SSDs rival server HDD speeds while delivering 100x more IOPS.
  • QLC NAND pushes SSD affordability closer to HDDs.
  • Larger 2.5″ SATA SSDs up to 8TB compete on capacity.
  • 3D NAND stacking enables 32TB+ SSDs cost-effective for some servers.
  • Faster new storage like 3DXPoint challenges HDD tiering roles.

Client and enterprise SSD adoption surging over 50% per year proves those sectors favor solid state when priced competitively. The HDD value proposition now centers on economical bulk storage for cold data. As NAND costs decline further, HDDs will be pressed even there.

Conclusion

Hard disk drives face growing pressure from SSDs that beat them on speed, resilience, power, and increasingly, price. However, hard drives aren’t going away anytime soon. The advantages of mechanical storage like very low cost per terabyte ensure HDDs have an ongoing role in PCs, data centers, and other applications. Hard disk technology also continues evolving to stay cost competitive. While SSDs are capturing more of the market, traditional spinning hard drives remain essential for affordable high capacity storage.