Quick Answers
SSDs are faster, more durable, and more power efficient than HDDs. However, HDDs have much higher storage capacities and are cheaper per gigabyte.
For most everyday users, an SSD is the best choice for an external drive due to its speed and durability. HDDs are better suited for large backups and archives where capacity is crucial and speed is less important.
What is an SSD?
SSD stands for Solid State Drive. An SSD uses flash memory chips rather than spinning platters to store data. This allows SSDs to access data much faster than traditional hard drives.
Some key advantages of SSDs:
- Faster read/write speeds – Up to 10x faster than HDDs for sequential reads and writes
- Lower latency – No need to physically move drive heads, allowing near instant access to data
- More durable – No moving parts makes SSDs better able withstand drops and vibration
- Use less power – Up to 4x more power efficient than HDDs
- Compact and lightweight
However, SSDs also have some downsides:
- More expensive per gigabyte than HDDs
- Lower capacities available – Though capacities are rapidly increasing
What is an HDD?
HDD stands for Hard Disk Drive. HDDs use spinning platters coated in magnetic material to store data. A read/write head moves over the platters to access data.
HDDs have been the traditional standard for PC storage for decades. Some advantages of HDDs include:
- Much cheaper per gigabyte than SSDs
- Higher maximum capacities – 10TB+ HDDs are available
- Proven technology that has been refined over decades
However, HDDs also come with some downsides:
- Slower speeds – Data access requires physical movement of the drive heads
- Higher failure rates – The mechanical parts wear out over time
- Heavier and bulkier than SSDs
- More prone to damage from drops or vibration
- Use more power than SSDs
SSD vs HDD: Speed
SSDs are significantly faster than HDDs when it comes to data transfer speeds.
A typical SATA III SSD has sequential read speeds of around 500-550 MB/s. Write speeds are slightly lower, in the 400-500 MB/s range.
In comparison, a high performance 7200 RPM HDD will have sequential read/write speeds of around 100-160 MB/s. In other words, SSDs are 3-5 times faster for large file transfers.
SSDs have near instantaneous access times of 0.1 ms or less. HDDs require an average of 5-10 ms to move drive heads to locate data. This makes a huge different for small random data accesses.
Overall, SSDs will feel much snappier and responsive when loading programs, files, or booting up. Activities like copying files or installing software happen significantly faster.
SSD vs HDD: Durability
SSDs are much more durable and shock resistant than HDDs.
Because they have no moving parts, SSDs can withstand bumps and vibrations better. SSDs are not hurt by sudden power loss, whereas HDD heads can crash onto platters during a sudden shutdown.
Most SSDs are rated for 1.5 million hours Mean Time Before Failure (MTBF). Consumer grade HDDs are rated for around 1 million hour MTBF.
However, HDD failure rates increase quickly once a drive exceeds its design life. A HDD that has been heavily used for 3-5 years will be much more prone to failure than a new SSD.
For external hard drives which may get moved around frequently, SSDs are a safer bet to avoid potential drive failures. A dropped external HDD could easily damage internal components.
SSD vs HDD: Capacity
HDDs offer much higher maximum capacities compared to SSDs.
Currently available SSDs max out at around 16 TB for high end models. External SSDs commonly top out at 4 TB.
HDD capacities go much higher, ranging from 10 TB on the consumer end to 20 TB for enterprise class drives. Currently available external HDDs commonly offer 6-10 TB per drive.
If you need a high capacity external drive for backups or media storage, HDDs will be better suited for the job. The cost per terabyte is significantly lower compared to SSDs.
However, also consider whether transferring and managing such large amounts of data would be realistic over USB 3.0 or USB-C interfaces, which max out at 625 MB/s.
SSD vs HDD Cost Comparison
| Drive Type | Price Per GB |
|---|---|
| 250GB SATA SSD | $0.15 – $0.25 |
| 1TB SATA HDD | $0.03 – $0.04 |
| 2TB External HDD | $0.025 – $0.035 |
| 4TB External SSD | $0.20 – $0.40 |
As you can see, HDDs are significantly cheaper in terms of cost per gigabyte. 4TB external SSDs cost around $800, while 4TB HDDs cost between $100-150.
However, also consider how many years you may use a drive. HDDs degrade in performance over time and have higher failure rates after 3-5 years. An SSD should last at least 5 years with reasonable use.
Spreading the cost over the usable lifespan makes SSDs more competitive. Nonetheless, HDDs will be the budget drive of choice when capacious amounts of storage are needed.
Ideal Uses for External SSDs
External SSDs shine for the following use cases:
- Frequent travel – With no moving parts, SSDs better withstand travel environments
- Quick data access – SSDs provide much faster file transfers and loading
- Rugged environments – Vibration, dust, humidity, and shock resistance give SSDs an edge
- Frequent plugging/unplugging – SSDs can better handle connection cycles
- Heat management – SSDs produce very little heat compared to HDDs
- Noise reduction – SSDs are silent since they lack spinning platters
If speed, durability, and noise levels are priorities, an external SSD will serve you better even if you pay a premium.
Ideal Uses for External HDDs
External HDDs are a good choice in these scenarios:
- Backups and archives – The large capacities are perfect for backups
- Media libraries – Store your photos, videos, and music libraries
- Gaming storage – Provide abundant storage for games on PCs and consoles
- Non-essential data – Use as expanded storage for non-critical files
- Cost-effective portability – Inexpensive option for portable file storage
If you simply need raw capacity for copies of files, media, games, or hobby projects, an external HDD gets the job done affordably.
Just be sure you are not storing your only copy of highly important data on an external HDD, as failures can happen unexpectedly. Always have a separate backup.
External SSD vs HDD: Drive Interface
The drive interface used by external storage devices also affects overall speed. Most portable hard drives use USB connections.
USB 3.0 provides a maximum bandwidth of 625 MB/s, which equates to 5 Gbps. This is 10 times faster than the USB 2.0 standard.
USB-C drives may use USB 3.0 speeds, or they may use newer standards with higher bandwidth:
- USB 3.1 Gen 2 – 1,250 MB/s
- USB 3.2 Gen 2×2 – 2,500 MB/s
- Thunderbolt 3 – Up to 5,000 MB/s
Pay attention to whether your computer or device has USB-C ports that support these faster protocols if speed is important. Otherwise, peak transfer rates will be limited to USB 3.0 speeds.
The fastest external SSDs can nearly saturate a USB 3.0 connection. But HDDs cannot reach USB 3.0 limits, so their maximum performance is reduced.
External SSD vs HDD: Performance Consistency
Another advantage of external SSDs over HDDs is performance consistency. HDD speeds fluctuate greatly depending on where data resides on the drive platters. Data stored on the outside edges of platters will transfer much faster than data on the inner edges.
SSD performance stays more consistent regardless of which memory blocks data is stored in. This leads to smooth data transfers at low queue depths.
HDDs can sometimes spike in transfer speeds when the drive cache and request queues are filled up, but this is not representative of typical usage. In real-world tasks, external SSDs provide faster average transfer rates.
Shock and Vibration Resistance
By design, HDDs are highly prone to errors caused by shock and vibration forces. The precision required to quickly move drive heads nanometers above platters is disrupted by even small impacts.
Dropping a powered hard drive from just a few inches can cause the drive head to bang down on the platter surface, leading to irreparable damage. Vibrations during data transfer introduce errors and performance degradation over time.
SSDs have no moving parts, making them far more resistant to shock damage. Drops that would destroy HDDs have almost no effect on SSDs. This is a key factor in their favor for external portable drives.
Vibration resistance is also superior with SSDs. Sustained vibrations still wear down the flash memory cells over an extended period. But performance remains high in typical consumer environments.
Altitude and Temperature Tolerance
HDDs function best under normal atmospheric pressure at sea level. Higher altitudes with lower air pressure compromise the air bearing that allows drive heads to float just above the disk platters.
This makes HDDs more prone to errors at altitudes of 10,000 ft and higher. Pressurized enclosures are required for high altitude use.
Temperature fluctuations also impact HDD performance and reliability. Operating HDDs outside the optimum range of 5°C to 55°C introduces possible errors.
SSDs work reliably across a much wider range of temperatures from -40°C to 85°C. Variable air pressure at high altitudes does not affect SSD operation.
For these reasons, SSDs are a more robust choice for use in harsh environments and outdoor conditions. A solid state drive won’t flinch at high elevations or freezing temperatures.
Power Consumption
One area where SSDs shine is power efficiency, especially when looking at idle power. HDDs consume around 5-7 watts when sitting idle compared to just 2-3 watts for SATA SSDs.
The difference is even more substantial under load. A typical 3.5-inch HDD uses up to 7-11 watts during data transfer compared to 2-5 watts for a 2.5-inch SATA SSD.
The reduced power requirements give external SSDs a couple advantages:
- Extend battery life when powered from a laptop or tablet
- Generate less heat leading to cooler operation
This may not make a big difference for a desktop setup. But when running off USB power from a portable device, energy efficiency gives SSDs the nod.
External SSD vs HDD: Noise Level
A key benefit of SSDs is they produce minimal noise when operating. There are no spinning platters, moving heads, or motors to generate audible noise.
In comparison, the mechanical components of HDDs create low frequency noise during drive access and idle spinning. For desktop PCs, this is not much concern. But a loudly whirring external HDD when trying to sleep could be distracting.
Noise levels might not be a purchase consideration if the drive use is intermittent. But for continuous access to an external drive, an SSD running silent is preferable over the faint buzz of a HDD. This makes SSDs better choices as boot drives for home theater PCs and game consoles.
Failure Rate Comparison
All storage devices will eventually fail. But which technology lasts longer on average?
Consumer grade HDDs typically have a 2-3% annualized failure rate once a drive goes past its initial infant mortality period. Among the major manufacturers, Seagate drives see higher than average failure rates around 3%.
SSDs usually have lower annual failure rates in the 1-2% range. However, SSDs tend to offer shorter warranties at 3-5 years versus 3-10 years for HDDs.
For external portable drives, the MTBF ratings give an idea of expected lifespans under ideal conditions:
- Portable external HDD – 1 million hours MTBF
- Portable external SSD – 1.5 million hours MTBF
Overall, external SSDs likely have a small edge in terms of average annual failures given similar usage. But both technologies remain reliable for many years barring excessive shocks or misuse.
Fragmentation
File fragmentation on HDDs leads to gradual performance reduction over time. Files stored in many fragments take longer to access as the drive heads must physically seek out each fragment.
SSDs do not have this problem, so their performance stays consistent even after heavy long term usage. External SSDs will retain their speed advantage years down the line.
Defragmenting HDDs improves performance by consolidating file fragments. However, this process can take hours for larger hard drives. External SSDs never require defragmenting.
Encryption
Users who want physical encryption of their data will need to take extra steps with external hard drives. Software encryption adds computational overhead.
Many external SSDs include hardware-based AES encryption to secure data on the drive. Encryption keys are stored in dedicated security chips rather than main storage.
Hardware encryption has minimal impact on SSD performance. And it operates independently of the host computer, so risks like unencrypted wear-leveling are avoided.
RAID Support
An advantage of external HDDs is they commonly allow for RAID configurations through the drive enclosure. This allows using multiple physical drives as a single logical drive for increased speed or redundancy.
Most external SSD enclosures only include a single drive. There are higher end RAID enclosures available, but these cost more than a multi-drive HDD enclosure.
For home or small office use, JBOD RAID 0 HDD arrays can provide fast speeds for less cost compared to a RAID SSD setup. Just be sure to backup your data elsewhere.
Conclusion
Solid state drives are the superior choice for most external drive purposes besides cost effective bulk storage. The advantages of SSDs in speed, durability, power efficiency, and noise simply outweigh the downsides.
HDDs still serve an important role for mass storage needs. If your priority is reliably storing terabytes of media or backup archives, HDDs get the job done on a budget.
For everyday external storage, SSDs are worth the premium. Plummeting flash costs continue to reduce the price gap between SSD and HDD storage over time.