U.2 and U.3 SSDs are both designed for enterprise storage, but they serve different needs. Here’s the quick takeaway:
- U.2 SSDs: Support only NVMe, use the SFF-8639 connector, and are ideal for setups focused on NVMe performance. They come in 7mm and 15mm sizes and offer capacities up to 30.72TB.
- U.3 SSDs: Add tri-mode support (NVMe, SATA, SAS) with the SFF-TA-1001 specification, making them more versatile. They are backward-compatible with U.2 systems but not the other way around.
Quick Comparison
| Feature | U.2 SSD | U.3 SSD |
|---|---|---|
| Protocol Support | NVMe only | NVMe, SAS, SATA |
| Backward Compatibility | Limited | Works with U.2 bays |
| Connector | SFF-8639 | SFF-TA-1001 |
| Form Factor | 7mm, 15mm | 7mm, 15mm |
| Host Compatibility | U.2 systems only | U.2 and U.3 systems |
Key takeaway: Choose U.2 for NVMe-focused systems and U.3 for flexibility across protocols. Both options are reliable for enterprise workloads, but U.3 offers more future-proofing with its tri-mode design.
Technical Details
U.2 SSD Design
U.2 SSDs follow the 2.5-inch form factor and use the SFF-8639 connector to ensure PCIe compatibility. They support multiple power delivery options (3.3V, 5V, and 12V), making them suitable for enterprise setups [4][5]. The design integrates PCIe lanes while remaining compatible with existing storage systems [1].
U.3 SSD Design
U.3 SSDs build on PCIe connectivity by adding advanced features [6]. They include two IfDet pins for automatic detection of the host interface [6]. This design allows tri-mode support - SATA, SAS, and NVMe - through a single drive bay, streamlining management by removing the need for separate components for each protocol [6]. These updates highlight the differences in design, as outlined below.
Design Differences
Here are the main design differences between U.2 and U.3 SSDs:
- Interface Detection: U.2 uses one IfDet pin, while U.3 employs two for better protocol detection.
- Protocol Management: U.2 requires individual controllers for each protocol, whereas U.3 uses a unified controller for all.
- Host Compatibility: U.2 supports specific protocols, while U.3 provides tri-mode support (SATA, SAS, and NVMe).
- Infrastructure: U.2 relies on multiple backplanes, but U.3 consolidates this into a single backplane.
U.3's ability to re-map high-speed lanes allows smooth protocol switching, a key feature for modern enterprise needs. Industry reports suggest NVMe SSDs might account for over 75% of enterprise deployments [7]. While U.3 drives are backward-compatible with U.2 hosts, U.2 drives cannot function in U.3 drive bays due to differences in pin configurations and protocol support [3].
HPE Server Support
U.2 Server Support
HPE ProLiant servers accommodate U.2 SSDs across multiple generations. The DL385 Gen10 offers configurations with 8, 12, 16, or 24 drive bays, providing flexible storage options. For high-performance tasks like virtualization, AI, and machine learning, the DL360 Gen10 Plus stands out with its NVMe-only setup and 10 drive bays.
U.3 Server Support
The HPE ProLiant DL385 Gen11 servers now support U.3 SSDs, offering impressive storage capacity. With 15.36TB NVMe SSDs in a 24 + 8 + 2 drive bay setup, these servers can deliver up to 522.24TB of storage [8]. Keep in mind, mixing SAS, SATA, and NVMe SSDs can lead to performance issues, so maintaining consistent storage technology is essential.
Cross-Generation Support
Understanding how U.2 and U.3 SSDs work together across generations is crucial. U.3 SSDs use Host Port Type (HPT) pin combinations to ensure compatibility with U.2 hosts. Here’s a quick look at compatibility scenarios:
| Compatibility Scenario | Support Status | Key Considerations |
|---|---|---|
| U.3 SSD in U.2 Host | Supported | Requires correct HPT pin configuration |
| U.2 SSD in U.3 Host | Not Supported | Hardware incompatibility |
| U.3 SSD in U.2 System | Limited | May need verification of pin connections |
When using U.3 SSDs in a U.2 environment, double-check that HPT pins, adapters, and PCIe lanes are set up correctly. PCIe Gen4 Data Center NVMe SSDs outperform SAS drives by up to 5.8× and SATA drives by up to 13.3× [2].
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Speed and Performance
Let's dive into the performance metrics that make U.2 and U.3 SSDs well-suited for enterprise workloads.
Data Transfer Rates
U.2 SSDs operate on the PCIe 3.0×4 bus, offering a theoretical bandwidth of up to 32Gbps [9]. For instance, the Intel 750 U.2 SSD (1.2TB) delivers sequential read speeds of up to 2,400 MB/s and write speeds of up to 1,200 MB/s. It also handles around 440,000 random read IOPS and 290,000 random write IOPS [9]. On the other hand, U.3 SSDs use a unified protocol to ensure consistently high-speed performance, making them a strong choice for demanding tasks.
Lifespan and Durability
Both U.2 and U.3 SSDs are built for reliability in enterprise environments. They come with a Mean Time Between Failure (MTBF) rating of at least two million hours - equivalent to over 230 years of operation [10]. Additionally, they experience only one unrecoverable bit error per 10 quadrillion bits processed (about 1.11 petabytes), which is ten times better than standard client SSDs [10]. Features like power-loss protection, advanced error correction, encryption, and S.M.A.R.T. monitoring further ensure data integrity for critical applications [10].
Energy Usage
These drives are designed to balance performance with energy efficiency. U.2 SSDs use the NVMe protocol to minimize overhead and reduce power consumption [9]. U.3 SSDs take it a step further by combining multiple protocols into a single interface, lowering overall energy requirements. This streamlined design helps reduce operational costs and energy use, making them a practical choice for data centers looking to optimize resources.
Best Uses
Both U.2 and U.3 SSDs are designed to tackle specific challenges in enterprise environments. With their performance strengths outlined, here's how each type can meet particular operational demands.
U.2 SSD Applications
The 15mm U.2 drives stand out for their large storage capacities - reaching up to 30TB - and hot-swappable design, which allows for maintenance without interrupting operations [13]. These features make them ideal for creative professionals like video editors and 3D animators, who need reliable, high-capacity storage to keep workflows running smoothly during demanding tasks [11].
Meanwhile, the 7mm U.2 SSDs offer a balance of performance and scalability, making them a great fit for enterprise IT setups. They perform well in VMware environments and RAID configurations, where consistent performance and quick storage provisioning are critical [13]. As data centers evolve, U.3 SSDs build on these strengths by adding more protocol flexibility.
U.3 SSD Applications
U.3 SSDs shine in modern data centers, thanks to their ability to support multiple protocols. They can seamlessly integrate with SAS, SATA, and NVMe interfaces within the same server slot [14].
"HPE NVMe High Performance Mixed Use (MU) SSDs are best suited for high I/O applications that require a balanced performance between reads and writes to deliver high performance and endurance for data intensive applications." [12]
Here’s how U.3 SSDs perform across different scenarios:
| Application Type | Benefits | Typical Use Case |
|---|---|---|
| Big Data Analytics | High I/O performance | Real-time data processing |
| HPC Workloads | Balanced read/write speeds | Scientific computing |
| Virtualization | Consistent performance | Multi-tenant environments |
HPE's U.3 SSD models are rigorously tested, with 3.35 million hours of testing and qualification [12]. They also feature digitally signed firmware to enhance security by preventing unauthorized access [12].
For data centers with high-density storage needs, 7mm U.3 SSDs provide efficient performance while consuming less power. On the other hand, 15mm U.3 SSDs are tailored for large-scale setups, offering maximum storage density and reliability [13].
Conclusion
Main Points
The U.2 interface set the stage for NVMe performance, while U.3 builds on it by adding tri-mode support. U.2 SSDs are designed for NVMe in a 2.5" form factor, whereas U.3 SSDs can handle NVMe, SAS, and SATA drives in the same bay [15]. Here's a quick comparison:
| Feature | U.2 SSD | U.3 SSD |
|---|---|---|
| Protocol Support | NVMe only | NVMe, SAS, SATA |
| Backward Compatibility | Limited | Works with U.2 bays |
| Form Factor Options | 7mm and 15mm | 7mm and 15mm |
SSD Selection Guide
When deciding between U.2 and U.3 SSDs for HPE ProLiant servers, keep these points in mind:
-
Choose U.2 SSDs if:
- Your setup is focused solely on NVMe protocols.
- You need reliable, proven performance.
- Hot-swappable drives are a must-have for your workflow.
-
Choose U.3 SSDs if:
- You require support for NVMe, SAS, and SATA in one solution.
- Future-proofing your storage infrastructure is a key goal.
- Simplifying inventory management with universal drive bays is important.
Next Steps in SSD Tech
U.3 SSDs bring greater protocol flexibility and improved performance, guided by the SFF-TA-1001 specification. This ensures compliance with current standards while paving the way for future developments. With this standardization, HPE ProLiant servers can consistently deliver across various workloads, from big data analytics to virtualized environments.
As storage demands grow - both in density and flexibility - U.3's tri-mode capability positions it as a key solution for the next generation of enterprise storage.
