SFF-8482 to SATA

[MystikIncarnate]

I’m kind of falling down a rabbit hole and I’m not sure I understand why this doesn’t exist. I would think that there’s a good reason, but I have no idea what that might be.

Long story short, since most SAS controllers also support SATA, why don’t we see a SATA only M.2 carrier board for two m.2 drives, with a dual port SAS connector?

Each SAS connection on the standard SAS drive interface (I’m pretty sure this is the SFF-8482), should be able to support SATA, and there’s plenty of cable options to plug internal SAS connectors (4x or 8x or whatever) to an appropriate number of SATA plugs. But if you’re using an array with dual links to a SAS compatible backplane, the second cable is basically unused if you’re using SATA drives.

The only apparent solution is to add another backplane/drive tray and wire the second SAS interface to it. This solution works, as far as I’m aware, but raises the question of why wouldn’t it work the other way.

Basically having two SATA drives on a carrier board (SATA M.2 to 2.5" form factor change type carrier) with two M.2 slots, each goes to their respective port on the SFF-8482 connector, both pulls power from the single power supply via the 8482 connector.

Such a thing seems like it should be possible, but there doesn’t seem to be any such product that exists. There’s a lot of strange and interesting 2.5" M.2 carrier boards out there, but this one seems to be missing.

It would be an easy way to add extra storage to a system with limited drive bays.

As far as I know, the second drive link on a SAS drive is mainly for redundancy, in case the first link fails or in case the controller on that link fails, but in circumstances where both links go to the same controller (and especially in cases where they don’t), there’s no option to add a second drive for the second link, which expands the drives that are accessible but reduces the overall redundancy/capacity of the system.

When I’m looking at the SATA drives in my Dell systems, all drive bays are full, but only half of the ports available on the controller are occupied. Presumably for dual link drives. I can buy a SAS breakout cable and add drives but I don’t have space in the system to put them.

I’m just confused why this isn’t a product that can be purchased. I’ve been looking at my storage situation and I’m just baffled. Some connectors are fully utilized, having more disks on the cable than there are SAS links, and yet others in the same system have zero drives on them?

Seems like a no brainer. Just add drives. Make the dual link SAS interface into two SATA interfaces and done, right? Such a product doesn’t exist.

Help me understand.

[twin_savage]

@MystikIncarnate

why don’t we see a SATA only M.2 carrier board for two m.2 drives, with a dual port SAS connector?

I haven’t seen one of these either, and I wouldn’t expect to with m.2 SATA being dead/depreciated for many years.

Another reason this wouldn’t make financial sense is that almost all dual port SAS connections are done through expanders (i think microchip is the only company selling dual port cables), and I don’t think expander firmware is going to allow for different luns out of different ports.
I’m certain there wouldn’t be compatibility problems if dual port cables>controller were used on a hypothetical dual sata carrier board though, but dual port cables are ultra rare.

[MystikIncarnate]

I wasn’t aware that SATA M.2 was deprecated. That’s new to me.

It certainly would explain the void in the market for SATA M.2 based stuff though.

Certainly a backplane could be engineered that supports it, but it would be a niche item in a dead/dying market space. AFAIK, the backplane I’m dealing with only does port expansion where all port 1’s off every drive goes to the internal SAS 1 connector, and the same for port 2, so I would think this would work with the existing technology, but as I’ve hopefully made it clear, I don’t know enough about it to confidently say what the challenges there might be.

I learn something new every day. Thanks.

[twin_savage]

I suppose depreciated is kind of a vague term, but what I mean is that the port is no longer being included on many new motherboards and I’m not seeing any new drives come out for the form factor/interface. Heck there are quite a few new motherboards that still offer parallel ports on them but I also consider that a depreciated port.

I’d be most concerned how the the backplane’s expander’s firmware handles unique luns when it is expecting only one lun from both ports.
The inverse problem exists on backplanes too for some of the fast SAS SSDs that combine both SAS ports to increase bandwidth to twice original speed, not all expanders support this.