Internal vs External HD MiniSAS: What’s the Difference?

If you’re building or upgrading a data system, HD MiniSAS cables are likely on your radar. But before you buy, it’s important to know: there are two distinct types, internal and external, and they are not interchangeable. Both use high-density SFF-8643 and SFF-8644 connectors, respectively, but they serve very different roles.

Let’s walk through the key differences.

1. Connector Types: SFF-8643 vs. SFF-8644

• SFF-8643 is the internal HD MiniSAS connector. It’s compact and optimized for tight, enclosed environments like inside a server or storage array.
• SFF-8644 is the external version. It’s larger, includes a metal housing, and is designed to withstand environmental exposure and frequent plugging/unplugging.

Don’t try to use one in place of the other, they won’t fit, and they aren’t electrically compatible.

2. Cable Construction

• Internal cables (SFF-8643) are usually shorter and more flexible. They connect devices within a chassis like motherboard to backplane, or controller card to drive cage.
• External cables (SFF-8644) are shielded, often with robust locking mechanisms. They're made to connect systems to systems, like from a host server to a JBOD.

External cables often have more rugged jackets and tighter tolerances for EMI shielding.

3. Typical Use Cases

4. Performance and Protocol Support

Both internal and external HD MiniSAS cables support:

• SAS 2.0, 3.0, and 4.0
• PCIe Gen 3.0 (in some configurations)
• Data rates up to 12Gbps per lane

The performance is largely dictated by cable quality, length, and connector integrity, not whether the cable is internal or external.

5. Mistakes to Avoid

• Don’t try to route an internal cable outside the chassis. It’s not shielded or rugged enough.
• Don’t assume “HD MiniSAS” means one connector fits all. Always check for SFF-8643 vs. SFF-8644 in specs.
• Don’t mix internal and external cables in the same run. They’re designed for different port types.

When in doubt, ask for clarification. Many system builders assume MiniSAS means backward compatibility or cross-functionality but in the case of internal vs. external, that’s a costly mistake.

FAQ (Frequently Asked Questions)

What’s the difference between SFF-8643 and SFF-8644?

SFF-8643 is the internal HD MiniSAS connector used inside systems. SFF-8644 is the external version with a more rugged design for cable runs between systems.

Can I use an internal HD MiniSAS cable externally?

No. Internal cables are not shielded or ruggedized for external use. Doing so risks EMI issues and premature failure.

Are internal and external HD MiniSAS cables interchangeable?

No, they have different connectors and use different ports. Always match the cable to the port (8643 for internal, 8644 for external).

What protocols do these cables support?

Both support SAS 2.0, 3.0, 4.0, and in some configurations, PCIe Gen 3.0 signaling.

How do I tell which one I need?

Check where the cable is going, if it’s staying inside a chassis, you need SFF-8643. If it connects to an external enclosure or JBOD, go with SFF-8644.