You are correct on the three most common external connectors used for
SAS-1, 2, and 3. One thing to note is the SFF-8470 is also known as a CX-4
connector, used for 10Gbps Ethernet by some older equipment.
All three SFF port types have been used with both active optical, up to
10m, and passive copper, up to 3m, cables. Same with the SFP+ and QSFP+,
though usually these are only seen on one end of the cable.
SAS is backwards compatible across the line, for example a SAS-3 compatible
drive bay can accommodate a SAS-3, SAS-2, or SAS-1 drive. I actually have
this in use with a SAS-3 HBA running SAS-2 tape drives. Drive and
controller firmware are the only issues that may prevent some SAS-1 drives
from working in SAS-2 or SAS-3 bays.
The minor versions, SAS-1.1 or SAS-2.1, use the same port types and cables
as their .0 parents. The only real difference was in firmware and some
Breakout cables are available with one connector splitting into up to 4
cables. These are almost never used for HDD/SSD SAS expanders but are used
with tape drives. They can have any connector type needed. Two currently
available common examples are one SFF-8644 to four SFF-8088, and one
SFF-8088 to four SFF-8088.
Lastly there is no configurable/visible addressing with SAS. Functionality
wise in Racktables external SAS should act more like power ports and cables
than network ports and cables.
On Sun, May 15, 2022 at 5:54 AM Denis Ovsienko <denis@xxxxxxxxxxxxx> wrote:
On Fri, 13 May 2022 17:22:12 -0400
"Chris Woelkers - NOAA Federal" <dmarc-noreply@xxxxxxxxxxxxx>
Specifically external SAS, both SFF-8088 and
My experience with SAS is rather limited, and I didn't pay attention to
the standard versions before, so I would need some additional input to
get this matter right. As far as it is possible to tell from some
online documentation, the most common use cases for external SAS
connectors are the following copper cables:
* SFF-8470 termination for SAS-1
* SFF-8088 termination for SAS-2
* SFF-8644 termination for SAS-3
Less common, yet valid use cases seem to be SFP+ and QSFP+ termination
for copper cables (SAS-2) and SFF-8644 termination for active optic
assemblies (SAS-2.1 and SAS-3). Is there anything else?
Regarding backward compatibility, I found some tech support articles
claiming SAS-3 is compatible with SAS-2 and SAS-2 is compatible with
SAS-1, regardless of which end is the initiator and which is the
target. Is this always true and does the same stand for SAS-1 and
Also would it be correct to say that the only difference between SAS-1.0
and SAS-1.1, as well as between SAS-2.0 and SAS-2.1, is in the protocol
details that are specific to the firmware (i.e. can change later)? Are
SAS-1.1 and SAS-2.1 distinct enough to be worth using their own port