SAS, Mini-SAS and Mini-SAS HD Assemblies

There is one compatibility rule in storage that runs in only one direction, and getting it backwards costs a build. A SAS controller will host a SATA drive. A SATA controller will never host a SAS drive — the connector fits, and the drive does not initialize. Everything else on this page follows from that asymmetry.

What is the difference between SAS and SATA?

Three things in that table are commonly got wrong, including by people selling cable.

Full duplex is not a SAS differentiator. Serial ATA Revision 3.4 states plainly that the SATA link is a full duplex point-to-point link. You will see comparison tables — many of them — presenting half-duplex SATA against full-duplex SAS. That is wrong, and we are not going to repeat it to sell you a SAS cable. SAS differentiates on dual porting, queue depth, expander support and cable reach.

"SATA III" is not a SATA-IO term. The 6.0 Gb/s speed grade is Gen3 — Gen3i for internal. Revisions 3.0 through 3.4 are document revisions of the specification, not speed grades, and the two get conflated constantly. If a supplier quotes you "SATA III" they are using shorthand; ask which speed grade they mean.

Queue depth 32 is a ceiling, not a promise. NCQ supports tags 0–31 as the protocol maximum. The depth a given drive actually reports comes from IDENTIFY DEVICE Word 75 and can be lower.

SAS-4 adds 128b/130b encoding with 20-bit forward error correction.

Can you plug a SATA drive into a SAS controller?

Worth reading twice.

SAS domains can accept SATA drives through the Serial ATA Tunneled Protocol. One qualifier that matters on a real build: STP support is optional and defined at the SAS domain level. It is not guaranteed by every controller or backplane, so confirm it for your specific hardware rather than assuming it because the infrastructure is SAS.

SATA-only controllers and backplanes cannot address SAS drives at all. A SAS drive inserted into a SATA-only backplane will not initialize. Physical fit is irrelevant, and there is no optional feature that changes this one.

Practical consequence for a mixed deployment: a SAS-capable server can run SAS drives for performance-critical roles and SATA drives for bulk capacity on the same controller and backplane. The reverse is not available to you.

Why is a pin count not enough to identify a Mini-SAS cable?

Mini-SAS connectors are commonly referred to by pin count. That shorthand is ambiguous, and it is the most frequent source of a wrong specification reaching us.

Three things to take from that table, and the third is the one that costs money.

The numbering does not follow a pattern. 26P is SFF-8088 and 36P is SFF-8087, but 32P is SFF-8484 — not another 808x. A pin count cannot be converted to an SFF number by inference.

Most of these standards define more than one size. SFF-8087 alone covers four circuit counts. SFF-8643 and SFF-8644 cover three each. So naming the SFF number without the variant is only half a specification.

And a pin count can point at more than one standard. Both SFF-8087 and SFF-8643 have a 36 variant. A 68-circuit SFF-8087 exists alongside SFF-8639's 68 contacts. So neither "36-pin" nor "68-pin" identifies a connector — not ambiguously, not loosely, not at all.

> Always state the connector family alongside the pin count. Never the pin count alone.

Send us "Mini-SAS 36P" and we will come back with a question — is that SFF-8087's 36-circuit variant, or SFF-8643's? Send us "Mini-SAS HD SFF-8643, 36-contact" and we can quote. That one extra word is the difference between a cable that works and a cable that fits.

Is Mini-SAS HD a path to 24G SAS?

This is the correction most likely to save someone a wasted build.

Mini-SAS HD is a 12 Gb/s connector. SFF-8643's own specification rates it to 12 Gb/s, and SFF-9402 classifies it as Legacy. It is not a SAS-4 path, and specifying it for one will not get you there no matter what the cable is made of.

SAS-4 paths are SlimSAS and MiniLink. If your build targets SAS-4, that is where to look.

Internal Mini-SAS HD is SFF-8643, unshielded, defined at 36, 72 and 144 contacts. External is SFF-8644, shielded, defined at 36, 72 and 144. Separate specifications, not a matched internal/external pair of one standard.

A note on "24G". SAS-4 signals at 22.5 GBaud with 128b/130b encoding and forward error correction. "24G" is a marketing designation from the SCSI Trade Association, not an INCITS value, and baud rate is not payload rate. We use the term because buyers search it — but on a spec sheet it should read 22.5 GBaud.

SAS supports expanders for scaling to large drive counts and cascaded topologies. SATA does not.

Where does SAS, Mini-SAS or Mini-SAS HD belong in a build?

• SATA — cost-effective, high-capacity storage for desktops, NAS, home labs and bulk data tiers.
• SAS — enterprise storage needing high availability, dual-port redundancy, deep queuing, expanders and sustained multi-drive throughput.
• Mixed — SAS-capable infrastructure running both: SAS for performance roles, SATA for capacity.

What should you confirm before specifying a SAS or Mini-SAS assembly?

• A SATA controller or SATA-only backplane cannot host a SAS drive. Not even if the connector appears to fit.
• SAS and SATA drives do not perform identically — but full duplex is not the difference. SAS adds dual porting, deeper queuing, expander support and longer cabling. Both interfaces are full duplex.
• SATA support in a SAS domain is optional. STP is defined at the domain level and is not guaranteed by every controller or backplane.
• Mini-SAS HD is a 12 Gb/s Legacy connector, not a SAS-4 path.
• A "SAS-labeled" chassis does not guarantee a SAS-capable backplane. Some ship SATA-only. Verify the backplane and the HBA separately.
• Expanders are a SAS capability. Do not plan expander scaling on SATA.
• Form factor does not indicate interface. A 2.5" or 3.5" drive can be either.
• A pin count alone does not identify a connector. See the map above.

What SAS and Mini-SAS assemblies does EPS build to specification?

EPS manufactures SAS, Mini-SAS and Mini-SAS HD assemblies to your specification in Acton, Massachusetts, prototype through production — 10 to 10,000-plus units, QC tested. You specify length, conductor size (AWG), conductor colors, stranding, shielding (foil, braid or combination), jacket material (PVC, TPU, FEP, LSZH), temperature and environmental rating, overmolded boots, strain reliefs, latch and locking systems, and custom contact configurations. Y cables and multi-drop harnesses are built to the topology you specify.

Engineering review, then quote and approval, then manufacture and delivery. Lead time depends on the specification and the volume, and we confirm it with your quote. Long-term supply agreements support programs that need continuity.

Looking for a stocked part rather than a custom build? See available Mini-SAS parts at MicroSATACables.

What information does EPS need to quote a SAS cable?

1. Is the host controller or backplane SATA-only, SAS-capable, or hybrid SAS/SATA?
2. What drive type is being connected — SATA HDD/SSD, or SAS drive?
3. What speed target matters — 6.0 Gb/s (SATA Gen3), 12 Gb/s (SAS-3), or SAS-4 at 22.5 GBaud?
4. Which exact connector on each end, stated as family plus pin count?
5. Is dual-port redundancy, expander scaling or deep queuing required?
6. Are SAS and SATA drives being mixed in the same system?

Frequently asked questions