For most of computing history, mechanical hard disk drives (HDDs) served as primary storage thanks to high capacities and low costs. However solid state drives (SSDs) revolutionized storage performance by replacing spinning platters with integrated circuits. As SSDs now dominate client and data center segments, new interfaces and protocols like NVMe promise to again transform speed.
This article explains the key differences between established SATA SSDs and emerging NVMe technology. It compares capabilities across use cases and provides recommendations for matching storage to needs. After reading, you will confidently know whether to choose SATA or NVMe!
Storage Evolution Background
Before understanding next generation NVMe, we should explore the progress of SSDs. Flash memory pioneer Toshiba unveiled the first NAND SSDs for enterprises in 1991, but small capacities and high prices slowed adoption. In 2000, Samsung introduced consumer SSDs but faced similar restrictions keeping HDDs dominant.
From 2004, the SATA standard prevailed for connecting HDDs and early SSDs, providing up to 6 gigabits per second (Gb/s) bandwidth. Drives plug into a dedicated SATA port on the motherboard via a cable for data and another for power. The SATA protocol handles communication efficiently using queued commands.
Over a decade, Samsung, Intel, Micron and other NAND flash manufacturers improved density from SLC to MLC to TLC, increasing capacity while reducing cost per gigabyte. By 2016, SSDs accounted for 36% of storage revenue. Leading vendors now include Western Digital, Seagate, SK Hynix and Kioxia alongside controller developers Phison, Silicon Motion and Marvell.
With HDD speeds plateauing around 200 MB/s, mainstream SATA SSDs deliver over 550 MB/s read/write speeds. For consumer tasks like booting an OS, loading applications, transferring files and browsing websites, SATA SSDs far outpace HDDs. However modern workloads like gaming, creative media, data analytics and virtualization demand even greater performance.
In CONFIG.SYS days, storage relied on slow Programmed Input/Output (PIO) to communicate with systems. Later the SATA protocol stacked Advanced Host Controller Interface (AHCI) to enable Native Command Queuing (NCQ), allowing multiple outstanding requests. Nevertheless AHCI ties queues to each physical core, hindering scaling.
Enter NVMe, built to unleash the phenomenal bandwidth of PCI Express (PCIe) bus found in all modern CPUs.
Key Differences Between SATA and NVMe SSDs
While both serve as solid state storage media, from interfaces to software stacks, SATA and NVMe take radically different approaches.
Interface Bus and Speed
SATA connects drives over a dedicated cable with two lanes, one for transmit and one for receive. Bandwidth shared between devices peaks around 6 gigabits per second or 750 megabytes per second. Achieving those speeds requires a high end controller and careful NAND channel/die parallelism. Real-world SATA SSD speeds land between 450-560 MB/s.
NVMe directly leverages the underlying PCI Express interface built into all modern processors. PCIe dedicates point to point lanes called a link between the CPU and each device. Quadrupling lanes from x1 to to x4 or from PCIe 3.0 to PCIe 4.0 quadruples the bandwidth. Mainstream NVMe SSDs already take advantage of up to four lanes of PCIe 3.0 or PCIe 4.0 for peak transfer rates from 3.5-4GB/s. Future PCIe 5.0 should double this again!
| Specification | SATA | NVMe |
|---|---|---|
| Interface | AHCI Protocol over SATA | NVMe over PCIe |
| Link Configuration | Point-to-point | Point-to-point |
| Top Transfer Rate | 6 Gbit/s per lane shared | ~1GB/s per lane, often x4 lanes |
| Maximum Bandwidth | 600 MB/s shared | 4GB/s per x4 device |
| Cables | SATA Data and Power | None, slots directly into M.2 or U.2 bays |
| First Introduced | 2003 | 2015 |
This enormous bandwidth advantage fundamentally enables next generation SSD performance. Even implementing the NVMe protocol over dated SATA would fail to deliver such speeds. Accessing flash memory in parallel across PCIe unlocks tremendous throughput.
Software Communication
Efficiently coordinating data movement between operating systems and hardware relies on smart protocols, interfaces and drivers. AHCI served SATA drives well for over a decade by queueing requests instead of inefficient polling. However, AHCI ties queue depth to physical CPU cores, limiting capability of high core count systems.
NVMe defines a streamlined command set and queueing model that lifts restrictions by binding queues to threads. Systems assign multiple queues for each CPU core for deep queues supporting tens of thousands of commands. Efficient notification and event-driven polling minimize latency and overhead. This Scalable Queuing Model allows NVMe SSDs to fully saturate available bandwidth.
Specifically the NVMe driver embedded into operating systems communicates with an NVMe controller in the SSD over the PCIe link utilizing these queues. Requests get split into oppressively small commands of just 64 bytes. Newer NVMe standards further improve efficiency and reduce overhead on both hosts and devices through better fragmentation handling.
| Specification | SATA / AHCI | NVMe |
|---|---|---|
| Command Issuing | Up to 32 commands per queue | Up to 64K commands per queue |
| Queue Support | One queue per core | Many queues per core |
| Latency | Microsecond latency | Nanosecond latency |
| CPU Overhead | Higher overhead | Event-driven polling |
| Code Path | Legacy compatibility | Ground-up new |
Redesigned from scratch purely for nonvolatile memory components like SSDs, NVMe slashes latency while supporting parallelism. The host controller driver and device firmware now play a huge role in leveraging NVMe efficiently. Microsoft officially integrated NVMe drivers into Windows 8 and Windows Server 2012.
Physical Form Factors
The SATA interface generally powered 2.5” and 3.5” SSD form factors using well known drive bay sleds and cabling. M.2 and PCIe Add-in-Cards (AICs) connect via PCIe instead as early high performance NVMe drive packaging. However, M.2 rapidly became the de facto standard for consumer NVMe drives.
These tiny gumstick modules slot directly into an M.2 port on modern motherboards for a compact installation. Various lengths like 2242 (42mm) and 2280 (80mm) support smaller devices too. Importantly, M.2 supports either the SATA or PCI Express interface for both NVMe and AHCI SSDs. Always double check compatibility.
Many high capacity data center targeted drives adopt the 15mm tall U.2 (formerly SFF-8639) form factor. These still use the NVMe protocol over a PCIe link, but allow simple hot swapping into drive bays. Converting between U.2 and M.2 happens via inexpensive adapter cables or enclosures. Expect U.2 and M.2 to co-exist in servers for years with the latter dominating clients.
| Form Factor | Interface | Example SSDs |
|---|---|---|
| 2.5” Drive | SATA | Crucial MX500, Samsung 870 EVO |
| M.2 Module | SATA or PCIe | WD Blue SN570, Samsung 980 Pro |
| AIC Card | PCIe x4/x8/x16 | Intel Optane 900P |
| U.2 Drive | PCIe NVMe | Samsung PM1731a |
Power Efficiency
Pushing SSDs to their limits with heavy workloads increases power consumption, especially in bandwidth constrained SATA drives. The NVMe interface consumes around 2-4W more than a comparable SATA SSD. Per gigabyte, NVMe and SATA show remarkable parity however.
More importantly, remaining within that power budget while still delivering speed requires intelligent power management. PAHCI and DEVSLP allow connected AHCI devices to sleep and wake efficiently. Modern NVMe standards similarly specify hundreds of low power states while the Autonomous Power State Transition feature actively rotates through these depending on utilization to preserve performance.
| Specification | SATA SSD | NVMe SSD |
|---|---|---|
| Idle Power | ~2W | ~5W |
| Load Power | ~3W | ~7W |
| Power Management | PAHCI, DEVSLP | APST |
| Heat Output | Lower | M.2 may require heatsink |
In laptops and tablets, power draw directly impacts battery runtimes. So Apple Macbooks still use SATA while Microsoft Surface devices lean towards NVMe. Manymotherboards for desktop NVMe SSDs now integrate heatsinks onto the M.2 sockets too. Consider cooling for any high performance storage.
Real-World Performance
Synthetic benchmarks help marketers boast about maximum interface bandwidths. But end user experiences depend on sustained read/write throughput and responsiveness executing varied tasks. Comparing benchmark results on popular SATA and NVMe drives better predicts real world advantages.
Sequential Read and Writes measure streaming throughput when accessing large files continuously rather than random seeks. This resembles copying multi-gigabyte virtual machine images, databases, or video production assets. Top SATA drives max out around 560 MB/s, while high end NVMe SSDs reach over 5,000 MB/s thanks to interface multipliers!
However, consumer workloads often involve lots of little file or metadata operations. Random access resembles launching applications, loading game levels, or opening Office documents where small pieces of data get retrieved from all over the drive. Again NVMe dominates with over 400K IOPS compared to just 50-90K from SATA.
Finally mixed sequential and random benchmarking via application loading tests compare user experiences for booting Windows or Battlefront 2. Going from an HDD to SATA SSD easily halves load times. But NVMe saves another 25%, getting you gaming with your morning coffee!
| Benchmark | Top SATA SSD | High End NVMe SSD |
|---|---|---|
| Sequential Read | 560 MB/s | 7,000 MB/s |
| Sequential Write | 550 MB/s | 5,000 MB/s |
| Random Read IOPS | 90K | 440K |
| Random Write IOPS | 50K | 750K |
| Windows Boot | 15 seconds | 12 seconds |
| Game Level Load | 48 seconds | 35 seconds |
Clearly for large file manipulation or high IOPS workloads, NVMe blows past any SATA constraints. But even modest NVMe drives often double responsiveness over SATA competitors. Now we explore what system capabilities unlocked by NVMe enable these gains.
When to Choose NVMe
With mainstream SATA SSDs hitting 550MB/s reads, the interface bottleneck prevented most consumers benefiting from successive SSD controller and NAND iteration speeds boosting internal bandwidth into the GB/s range. Removing this barrier, NVMe empowers blazing fast storage.
Creative Workloads
Graphic artists, video editors, photographers, and 3D modelers constantly shuffle multi-gigabyte files. NVMe speeds import and export work significantly for formats like RAW, ProRes, or Arnold textures. Software compilation and genome sequencing see similar benefits working with huge data sets. NVMe also accelerates database analytics throughput.
Virtualization
Network administrators can provision more virtual machines (VMs) per host when using NVMe local instance storage. Faster virtual disk images enable devops flexibility. NVMe-oF extends this power through fabrics like Ethernet, Fibre Channel and Infiniband to disaggregated external storage.
Gaming and Multi-tasking
Quickly accessing overlays and textures from fast NVMe SSDs prevents stuttering in expansive open world titles like Cyberpunk 2077 or Microsoft Flight Simulator. NVMe also delivers snappier responsiveness when gaming while streaming music and web browsing simultaneously across [[[ disk regions.
Future Proofing
Rapidly evolving NVMe standards promise continued performance gains for years while SATA slowly sunsets. PCI Express bandwidth keeps growing alongside consistently denser NAND flash memory driving down $/GB. Get on the NVMe train to enjoy these advances!
When SATA SSDs Still Suffice
However, more moderate workloads would likely see minimal gains from NVMe‘s added expense. Everyday office productivity software and web browsing hardly tax SATA SSDs as is. Unless regularly handling multi-gigabyte files, NVMe provides almost exclusively bragging rights for huge benchmark bars rather than tangibly snappier user experiences.Network
Power users on older systems without spare PCIe lanes can still reap responsiveness benefits from SATA SSDs over HDDs too. Similarly for road warrior laptops, compact SATA SSDs generally claim better battery efficiency than M.2 NVMe drives. Size and compatibility also makes 2.5” SSDs easier for DIY NAS storage upgrades. While the tideshifts to NVMe across segments, SATA SSDs still deliver huge real-world improvements over slow HDDs for many.
The Future is NVMe
Industry trends clearly demonstrate NVMe and other PCIe SSDs represent the future while AHCI SATA retires. Leading software like Microsoft Windows, hypervisors like VMware ESXi, Linux distributions, and various appliances either support NVMe or soon will. Competing interfaces like SATA Express and NVMHCI failed to gain traction as NVMe quickly dominated thanks to broad ecosystem backing.
Upcoming platforms like PCIe 4.0 promise massive 8GB/s link bandwidth in high end systems while the PCIe 5.0 specification hits 128GB/s already! Low latency enhancements like TCP/IP offloads and NVMe-MI aim to further reduce overhead. Simultaneously NVMe-oF encapsulates NVMe storage commands efficiently over network fabrics instead of just PCIe. This clustering can scale performance, availability and capacity.
Contrast PCIe and NVMe momentum with SATA slowly fading. AHCI offers little room for speed gains moving forward while NVMe speeds leap ahead thanks to PCIe upgrades. Broader 6Gbit SATA adoption stalled as M.2 and U.2 directly leverage PCIe with NVMe. While SATA devices continue enjoying healthy shipments thanks to high capacities and friendly prices suitable for backups and secondary storage, peak performance clearly demands NVMe SSDs.
Conclusion
- NVMe SSDs unlock phenomenal speeds thanks to leveraging PCI Express bandwidth with an efficient queuing protocol communicating directly with CPUs
- Top sequential speeds exceed 7 GB/s reads and 5 GB/s writes over 4x PCIe 4.0 lanes while Intel Optane hits 1M IOPS
- M.2 form factor makes NVMe compact and convenient to install directly onto modern motherboards
- Workloads involving large files like 4K video production, creative assets, and databases benefit tremendously from NVMe
- Use cases requiring high random IOPS performance for accessing small files see big gains too thanks to NVMe queues
- For moderate everyday usage, SATA SSDs still offer huge improvements over hard drives at friendlier prices and power efficiency
- While SATA gradually fades away, rapid NVMe evolution will continue delivering blazing fast storage thanks to new NAND tech, upcoming PCIe 5.0 support, and data fabrics
So next time your game takes eons loading or file exports cripple productivity, consider upgrading to a zippy NVMe SSD!
