OpenSFF Enclosure Specification

5. Mechanical Layout and Slot Guidelines

OpenSFF enclosures MUST implement standardized slot layouts, connector alignment, and structural supports to ensure mechanical compatibility, serviceability, and reliable operation.

5.1 Slot Requirements by Enclosure Type

All OpenSFF enclosures MUST:

• Include one or more compute node slots using the Core (4C+) connector
• Maintain correct connector alignment, spacing, and mechanical support
• Provide unobstructed service access to all node and management module slots
• Support either vertical or horizontal slot orientation (vendor-defined)
• Support blind-mate alignment and node retention as defined in the OpenSFF Compute Node Specification (Section 3.4)

Enterprise Enclosures MUST:

• Provide both the Core and Enterprise connectors at each node slot
• Include a dedicated management module slot as defined in Section 3.2
• Implement shared infrastructure for power, internal networking, and KVM routing
• Support hot-swappable redundant PSUs and meet chassis-level airflow requirements, as defined in Section 4

Core Enclosures MUST:

• Include at least one node slot using the Core (4C+) connector
• Deliver adequate power and meet chassis-level airflow requirements, as defined in Section 4
• Expose basic I/O (USB, DisplayPort, Ethernet) externally for each compute node

5.2 Slot Geometry and Retention

The mechanical dimensions, envelope clearances, and retention interface for both compute node slots and the management module slot are defined in their respective specifications:

• OpenSFF Compute Node Specification (Section 3)
• OpenSFF Management Module Specification

Enclosures MUST implement slots that conform to these specifications, including:

• Accurate connector positioning for blind-mate alignment
• Compatible threaded retention points for M4 thumbscrews
• Adequate mechanical stiffness and clearance for safe insertion and removal
• Tool-less access for all user-facing service operations

5.4 Clearance and Padding

To ensure safe installation tolerances, mechanical stability, and adequate airflow between adjacent nodes and chassis structures, the following minimum clearances SHALL be maintained:

• A minimum of 5 mm of unobstructed space MUST be provided between each compute node’s outer boundary and the enclosure’s internal walls (top, bottom, left, and right).
• The same 5 mm minimum spacing SHALL apply between adjacent compute node slots, measured from the nearest mechanical edge of each node or its guide rail interface.
• Padding tolerances MAY be increased by vendors, provided node interoperability and alignment are not affected.

5.4 PCB Guide Rail Requirements

All OpenSFF enclosures MUST implement guide rail structures to ensure robust alignment, prevent connector wear, and improve shock and vibration tolerance during operation or transit.

Each compute node slot MUST include two vertical guide rails, positioned along the left and right edges of the node bay. These guide rails MUST:

• Engage only the reserved mechanical clearance zones defined in the OpenSFF Compute Node Specification, Section 3.5.
• Extend from the rear of the slot toward the I/O shield, without interfering with service access or obstructing front-panel features
• Allow for repeatable, tool-less insertion and removal of compute nodes without damaging the PCB

Note: All clearance dimensions and mechanical keep-out zones for guide rail engagement are defined in the Compute Node Specification and MUST be matched by the corresponding enclosure-side rail geometry.