TL;DR
Flash memory is generally faster than HDD for most typical consumer workloads. However, HDDs can outperform flash memory in certain niche scenarios like sequential writes of very large files. Overall, flash is superior for the average user.
Opening summary
For most common use cases, flash memory provides much faster performance than traditional spinning hard disk drives (HDD). The key advantages of flash include:
- Faster random read/write speeds – Up to 100x faster for random IOPS
- Lower access latencies – Flash access times are microseconds versus milliseconds for HDD
- Higher throughput for small block IO
- More resilient to physical shocks/vibrations
- Lower power consumption
- Silent operation
However, hard drives can outperform flash in some specific scenarios:
- HDDs are better for storing very large files sequentially – SATA SSDs max out ~500MB/s versus 150+ MB/s for HDDs
- HDDs offer significantly cheaper per GB storage costs
- HDDs can write data sequentially much faster than flash
For typical consumer workloads like booting an OS, launching applications, editing files, and multitasking between different tasks – flash is nearly universally faster due to its huge advantages in random IO performance and latency. HDDs are relegated to use cases like bulk photo/video storage and backups where sequential IO matters more. But for everyday tasks, flash memory is generally going to feel much faster than even the fastest spinning hard drives.
Flash Memory Overview
Flash memory stores data in memory cells made from floating-gate transistors. Each cell can store one or more bits of data using different voltage levels. Some advantages of flash memory include:
- Non-volatile – Retains data when powered off
- Solid state – No moving parts and very resistant to shock/vibration
- Low access latency – Read/write times in microseconds
- 3D V-NAND stacking for greater densities
- Lower power draw, allowing use in mobile devices
There are two main types of flash memory:
- NOR Flash – Used for code storage. Provides full address/data buses for random access reads. Writes are very slow.
- NAND Flash – Used for data storage. Provides higher densities but only sequential access. Much faster writes than NOR.
NAND flash is by far the most common flash today, used in USB drives, SSDs, and memory cards. It contains erase blocks of ~256 pages each. Writes can only be done sequentially within each block, but reads can access any page randomly. Garbage collection helps reclaim unused pages and consolidate data.
Flash Memory Scaling
Flash vendors have consistently scaled NAND flash to greater densities and lower costs per GB. Some ways they’ve achieved this include:
- Shrinking process nodes from 34nm down to 15nm and below
- Increasing bits per cell from SLC to MLC to TLC and QLC
- Stacking more NAND dies vertically – from 32 to 48 to 64+ layers
- Using larger page sizes – now 8KB, 16KB or larger
However these advances have also bought tradeoffs like lower write endurance and slower write speeds. Optimized controllers and program algorithms help compensate.
Hard Disk Drive Overview
Hard disk drives store data on quickly spinning platters coated in magnetic material. A head actuator positions read/write heads over the platters to access data. Some advantages of HDDs include:
- Very low cost per gigabyte
- Large capacities available – 10TB+ on consumer drives
- Fast sequential speeds – 150+ MB/s even on cheap drives
However, HDDs also have some downsides like:
- Much higher latency – Average seeks take ~10 ms versus ~10-100 us for flash
- Lower random IO performance – Drives max out ~200 IOPS versus up to ~600,000 IOPS for flash
- Fragile platters – Vulnerable to damage from shocks/vibration
- Higher power draw – ~5-10W idle and up to ~15W when spinning up
- Noise and heat from spinning platters
Hard Drive Scaling
HDD vendors have consistently grown aerial densities by advancing technologies like:
- Using smaller/tighter tracks towards 1 million tracks per inch
- Shifting from in-plane to perpendicular magnetic recording
- Employing shingled magnetic recording (SMR)
- Heat-assisted magnetic recording (HAMR)
- Using helium instead of air in sealed drives
However, HDD scaling is slowing down as technologies like HAMR and SMR face challenges. SSDs now exceed HDD densities and may be the future of high capacity drives.
Comparing Flash Memory and HDD Performance
Flash memory and HDDs take very different approaches to storing data, which results in huge performance differences:
Access Latency
Flash memory transistors can be accessed in microseconds – on the order of 10-100us for reads and 500-1000us for writes depending on technology. Hard drive heads must mechanically seek to a track and wait for the platter to spin under it. Average HDD seek times are generally 1-10 milliseconds.
This 1-2 order of magnitude latency difference makes flash feel much more responsive for things like booting an OS, launching programs, or loading game levels.
Random vs Sequential IO
Flash memory can read and write to any page randomly. HDDs must wait for the read/write head to move to the desired location mechanically. This gives flash a huge advantage in random IO:
| IO Type | Flash SSD | HDD |
|---|---|---|
| Random Read IOPS | Up to 600,000 | ~200 max |
| Random Write IOPS | Up to 600,000 | ~200 max |
However for sequential IO, HDDs read/write contiguous blocks on a platter much faster than flash pages:
| IO Type | Flash SSD | HDD |
|---|---|---|
| Sequential Read | Up to 3.5 GB/s | Up to 250 MB/s |
| Sequential Write | Up to 3 GB/s | Up to 250 MB/s |
So flash speed up random operations like booting an OS, launching apps, file editing, and multitasking. But HDDs are better for moving/copying large files sequentially.
Real-World Performance Comparison
Synthetic benchmarks provide insight into quantifiable metrics like latency, IOPS, and sequential throughput. But how do these differences translate into real user experiences?
Boot/Launch Times
Flash drives can boot computers in seconds rather than the minutes required by HDDs. Windows 8.1 booted 4x faster on average using SSDs versus HDDs. Game launch times see similar improvements.
File Copying
Copying larger files sequentially will be faster on HDDs. But for smaller files, flash maintains an advantage due to performing many small random reads/writes:
- Copying a 5GB ISO – ~2x faster on HDD
- Copying a 100MB music collection – ~5x faster on SSD
Video Editing
The random IO of video editing workflows favors SSDs over HDDs. Operations like importing clips or scrubbing through footage will see major speedups on flash. Exporting final videos leverages sequential write speeds where HDDs have an advantage.
Gaming
Faster level loading is one of the most noticeable benefits of flash for gaming. Games also do tons of small random reads when streaming textures/geometry from storage. This provides smoother frame rates and improved stutter on SSDs.
In essence, flash memory accelerates consumer experiences by reducing the time users spend waiting on their computers to load apps, files, and levels.
Reliability Comparison
Consumer flash drives and HDDs now both provide years of reliable service under normal usage:
- SSDs commonly rate for 5 years of endurance for writes per day (TBW)
- HDDs typically provide 550 TB of data written over 3-5 years
However, flash memory is inherently more resilient than HDDs. With no moving parts, it can withstand shock/vibration and function in more extreme environments. HDDs with spinning platters are fragile in comparison.
Data Retention
NAND flash slowly loses charge over time leading to potential data loss. High quality drives minimize this by periodically refreshing data:
- SLC flash retains data 10+ years
- MLC flash retains 5-10 years
- TLC flash 2-5 years
HDDs maintain data integrity indefinitely when powered on. Powered off, data may deteriorate on platters over time.
Cost Comparison
Hard drives continue to offer far lower costs per gigabyte than SSDs. Typical consumer HDD pricing is around $0.03/GB versus $0.20/GB or more for SATA SSDs. Here are some examples:
| Drive Type | Capacity | Price | Cost per GB |
|---|---|---|---|
| Seagate Barracuda HDD | 4TB | $90 | $0.0225/GB |
| Samsung 870 QVO SSD | 2TB | $200 | $0.10/GB |
Affordable SSDs narrow this gap with QLC NAND and aggressive caching. But HDDs remain much cheaper for high capacity bulk storage needs. SSDs are cost-effective for booting and running programs off of due to their huge performance benefits.
Power Efficiency Comparison
Flash memory consumes a fraction of the power required by mechanical hard drives. For example, a SATA SSD may use 2.5-3W when active and 100mW when idle. A modern HDD uses ~5-7W idle and up to 12W when spinning up the platters.
This matters for laptops where SSDs extend battery life by requiring much less power. But both are negligible for desktop use cases where other components dominate power consumption.
Noise is another consideration. HDD platters and head actuators make audible clicking and whirring noises when active. SSDs operate completely silently which is preferable for quiet computing environments.
Conclusion
In conclusion, flash memory provides vastly faster performance than hard drives for typical consumer workloads thanks to huge random IO improvements. HDDs are still preferred for use cases like:
- Archival storage
- Backup repositories
- Media server storage
But for booting, launching apps, browsing files, and everyday tasks – flash is king. The advent of affordable SSDs provides the biggest storage performance boost to consumer computing in decades. For the average user, flash memory is certainly faster than traditional spinning hard drives.