Quick Answer
USB 2.0 provides enough bandwidth for most hard disk drives (HDDs), but may limit performance compared to faster interfaces like USB 3.0 or eSATA. USB 2.0 has a maximum throughput of 480 Mbps, while mechanical HDDs typically max out below 200 Mbps. So USB 2.0 is adequate for basic external storage needs. However, for fast transfer of large files, SSDs, RAID arrays, or professional uses, a faster interface is recommended.
What is USB 2.0?
USB 2.0 is an interface standard for connecting peripherals to computers and other devices. It was released in April 2000 as an upgrade over the original USB 1.1 specification.
Some key characteristics of USB 2.0:
– Significantly higher maximum bandwidth than USB 1.1 – up to 480 Mbps vs 12 Mbps for USB 1.1.
– Full-duplex data transfers allow simultaneous sending and receiving of data.
– Backwards compatibility – USB 2.0 ports/devices can work with USB 1.1 at lower speeds.
– Plug-and-play connectivity that auto-configures when devices are connected.
– Provides power over the bus to low consumption devices. Up to 2.5W for each port.
USB 2.0 Transfer Speeds
The major advantage of USB 2.0 over 1.1 is the large increase in bandwidth:
– Low speed: up to 1.5 Mbps
– Full speed: up to 12 Mbps
– Hi-Speed: up to 480 Mbps
The Hi-Speed mode introduced in USB 2.0 is around 40 times faster than the original full speed rate. This enabled connections fast enough to support high bandwidth peripherals.
However, actual transfer rates are also limited by the speed of the USB controller and device. Many devices can’t reach 480 Mbps. A more typical maximum speed is 35-40 MB/s or 280-320 Mbps.
What is an HDD?
HDD stands for hard disk drive. It is a data storage device used in computers and many consumer electronic devices.
Some key features of HDDs:
– Use rotating magnetic platters to store data.
– Read/write heads move over the platters to access data.
– Non-volatile storage – data persists when power is removed.
– High capacity relative to cost. HDDs range from gigabytes to tens of terabytes.
– Sequential access where data is read/written in contiguous blocks.
There are two main types of HDDs:
Magnetic HDDs
– Traditional technology using magnetic platters.
– Typical speeds of 50-160 MB/s.
– Common in desktop PCs, game consoles, DVRs.
Solid State Hybrid Drives (SSHDs)
– Combines magnetic platters with NAND flash memory chip.
– Improves performance by caching frequently accessed data on flash.
– Speeds of 70-210 MB/s.
– Used in laptops and hybrid storage.
USB 2.0 Speed Relative to HDDs
The maximum bandwidth of USB 2.0 is 480 Mbps or 60 MB/s.
Most magnetic HDDs have sequential transfer speeds below 200 Mbps. Common speeds are:
| HDD Rotation Speed | Average Sequential Read/Write Speed |
| 5400 rpm | 75-120 MB/s |
| 7200 rpm | 100-160 MB/s |
| 10,000 rpm | 140-210 MB/s |
| 15,000 rpm | 200-250 MB/s |
So we can see even fast enterprise-class HDDs rarely exceed USB 2.0’s bandwidth.
SSHDs are faster, with max speeds from 70-210 MB/s. But many still fit comfortably within USB 2.0’s 480 Mbps.
Overall, the bandwidth of USB 2.0 is adequate for most HDDs on the market today. But there are some cases where USB 2.0 could bottleneck performance:
– Using multiple HDDs in RAID configurations can greatly increase speed beyond a single drive. A 4-disk RAID 0 array could easily exceed 480 Mbps.
– Solid state drives (SSDs) are much faster than HDDs, reaching 500+ MB/s. So USB 2.0 would severely limit SSD performance.
– Faster platter HDDs used in servers and NAS can exceed 200 MB/s and would benefit from more bandwidth.
Real-World USB 2.0 HDD Performance
While USB 2.0 provides enough theoretical bandwidth for HDDs, the real-world performance you see will depend on other factors:
– The speed grade of the USB 2.0 connection – some only support the original 12 Mbps full speed rate rather than 480 Mbps.
– Overhead from USB protocol and drivers takes 10-20% bandwidth.
– The HDD controller and cache architecture affects sustained transfer rates.
Typical real-world transfer speeds for a USB 2.0 HDD are in the 25-35 MB/s range. So you should expect to see:
– Large file transfers at 30-40 MB/s.
– Maximum throughput of around 280-300 Mbps.
– Long sequential reads/writes at 200+ Mbps.
For comparison, a USB 3.0 external HDD achieves 75-125 MB/s speeds. So about 2-3 times faster than USB 2.0.
USB 2.0 is fine for things like:
– Streaming media. Videos at 20 Mbps are no problem.
– Backing up your computer overnight. Transfer speed is less critical.
But for very large files or active workloads, USB 3.0 makes a big difference.
Should I Use USB 2.0 or USB 3.0 for an External HDD?
USB 2.0 provides enough bandwidth for hard drives, but has some limitations:
– Transferring lots of large files will be quite slow.
– Professional external storage needs like video editing require higher speed.
– SuperSpeed HDDs and SSDs are overkill on USB 2.0.
So while compatible, USB 3.0 is recommended for external hard drives when possible. The advantages are:
– Faster transfer of large files like videos, ISO images, photo collections, and disk images.
– Less time wasted when backing up TBs of data.
– Takes better advantage of high speed SSDs and enterprise HDDs.
– More headroom for future high bandwidth storage devices.
– Often a minimal price difference for USB 3.0.
There are some cases where USB 2.0 could still be sufficient:
– You only do light backups or move smaller files occasionally.
– The drive is mainly used for streaming media.
– You have an old computer and want to avoid adding a USB 3.0 card.
– Cost savings on USB 2.0 enclosures for less active storage.
So evaluate whether the 2-3x speed boost of USB 3.0 is worthwhile. It does provide a more future-proof solution as storage devices get faster. But USB 2.0 remains adequate for some lighter external storage needs.
Using HDDs with USB 2.0 vs. USB 3.0
Here are some tips for using HDDs efficiently with both USB 2.0 and USB 3.0 connections:
USB 2.0
– Fragment large files like ISO images or movie files into smaller parts to speed up transfers.
– Move files in batches to limit bottleneck from maxing out the USB channel.
– For active storage, look for drives with large caches to help sustain transfer speeds.
– Enable write caching if available to reduce the impact of slow write speeds.
– Consider SSHD drives to improve performance of frequently accessed data.
USB 3.0
– No need to split files – large movie files transfer quickly.
– Batch transfers are less necessary since bandwidth is plentiful.
– High speed SSDs can now maximize interface performance.
– Use multiple drives in RAID 0 for transfer rates exceeding 500 MB/s.
– Leverage USB 3.0’s speed to quickly backup a large photo library or video archive.
General Tips
– Update USB drivers and chipset drivers to ensure optimal USB performance on both interfaces.
– Try different USB ports on your computer – some may provide better performance than others.
– Use a short and high quality USB 3.0/2.0 cable to minimize signal loss.
– For desktops, add a PCIe USB 3.0 card if you have an older system without native USB 3.0 ports.
Conclusion
USB 2.0 has the bandwidth to support hard drives, but may limit performance compared to the speeds possible with USB 3.0 or faster interfaces like eSATA. For basic external storage usage, USB 2.0 is likely sufficient. But for professional environments or very large files, the extra speed of USB 3.0 is beneficial. While usable with HDDs, USB 2.0 is not optimal for SSDs or RAID configurations. So evaluate your specific needs, but upgrade to USB 3.0 when feasible to provide plenty of headroom for today’s high speed drives and ensure greater performance with future storage devices.
References
USB 2.0 Specification https://www.usb.org/document-library/usb-20-specification
USB 3.0 Specification https://www.usb.org/document-library/usb-30-specification-released-november-2008-and-revised-june-2013
Hard Disk Drive Performance Measurements https://web.cs.dal.ca/~jamie/csci3130/readings/hdd_measurements_toshiba.pdf
Serial ATA Native Command Queuing https://sata-io.org/system/files/member-downloads/NCQ_Overview.pdf
USB Storage Performance https://www.everythingusb.com/usb2/faq.htm
USB 3.0 Speed Difference https://www.pcmag.com/encyclopedia/term/usb-3-0
Choosing Between HDDs and SSDs https://www.pcmag.com/encyclopedia/term/54383/hdd-vs-ssd
