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Difficulty: Very hardStorage Devices and Interfaces

Match each storage drive interface specification or form factor standard with its correct hardware characteristic, physical keying requirement, or bus routing configuration.

  • M.2 Key BPhysically notched at pins 12–19; supports up to PCIe x2, SATA, and USB interfaces
  • M.2 Key MPhysically notched at pins 59–66; supports up to PCIe x4 and SATA interfaces
  • SATA Revision 3.2 (SATA Express)Combines two legacy SATA data connectors with auxiliary power/signal pins to deliver up to PCIe x2 bandwidth
  • U.2 (SFF-8639)A 2.5-inch form factor connector providing four PCIe lanes, SATA, and SAS compatibility with hot-swap support

Answer

M.2 Key B matches with the physical notch at pins 12–19 supporting up to PCIe x2 and SATA; M.2 Key M matches with the physical notch at pins 59–66 supporting up to PCIe x4 and SATA; SATA Revision 3.2 (SATA Express) matches with combining two legacy SATA connectors to deliver PCIe x2 bandwidth; U.2 (SFF-8639) matches with the 2.5-inch hot-swappable enterprise connector delivering four PCIe lanes.
Each storage interface specification is paired with its precise physical and architectural characteristics. M.2 Key B utilizes a notch at pins 12–19 and supports up to two PCIe lanes. M.2 Key M utilizes a notch at pins 59–66 and supports up to four PCIe lanes for high-speed NVMe storage. SATA Revision 3.2 (SATA Express) utilizes two standard SATA data ports along with additional control signals to route PCIe x2 bandwidth (~10 Gbps). U.2 (SFF-8639) provides a 2.5-inch hot-swappable interface capable of routing four PCIe lanes alongside legacy SATA and SAS signaling.

Step-by-Step Solution

1
Analyze M.2 keying pin allocations and bus lane constraints.
Identify that Key B is notched at pins 12–19 (limited to PCIe x2), whereas Key M is notched at pins 59–66 (supporting full PCIe x4 throughput).
Different M.2 pin notches dictate maximum PCIe lane allotment and socket compatibility.
2
Examine transitional bridging specifications between SATA and PCIe.
Recognize that SATA Revision 3.2 introduced SATA Express, which groups two physical SATA data ports with extra signals to provide two PCIe lanes.
SATA Express was developed to bypass the 6 Gbps limit of standard SATA III by utilizing PCIe lanes over a modified cable interface.
3
Evaluate enterprise 2.5-inch high-performance NVMe connectivity.
Determine that U.2 (SFF-8639) facilitates 2.5-inch drive hot-swapping while delivering four PCIe lanes along with SAS/SATA backplane support.
U.2 allows dense server backplanes to host PCIe NVMe drives with standard 2.5-inch drive trays.

Key Concept

Storage drive interface keying, bus routing, and connector specifications (M.2 Key B vs Key M, U.2, SATA Express)
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Topics

Storage Devices and Interfaces

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