Synology Backplane Design - SAS

[Robbie]

I'd don't usual peer down at the backplane so only just notice that my Synology NASes are fitted with SAS backplane connectors rather than the standard SATA-only design. The SAS B port side is even populated with pins too.

Is there any history or technical reason behind this choice or are SAS connectors just slightly cheaper so they just whack them on to a SATA board to save a penny or two?

 

[Coop777]

SAS drives have a higher RPM than SATA, hence faster, hence more expensive and used generally for enterprise environments.

 

[Robbie]

@Coop777 I'm entirely happy with what SAS drives are (although I would argue that the ability to duplex read/writes and double the bandwidth are the USP of SAS rather than platter RPM) - my technical 'surprise' is to find SAS backplanes on my Synology NASes.

 

[Samir]

I know this is a big necropost but there are no other threads on this exact subject.

I too just noticed on my new to me DS214+ and DS918+ that the connector is most definitely SAS. This is very strange as I know that for most applications, the physical sas connector costs more than sata.

So the bigger question is--can these units actually use sas drives? Has anyone tried it?

 

[Robbie]

No SAS for sure on the data backplane. I can only presume that it is cheaper to have SAS connections hammered-out by whatever company makes the board. The SATA-only version of this connection has long since departed from the enterprise space so the price delta, if any, is not worth changing the pick-and-place hoppers and tapes.

As to why SATA has not been replaced by SAS over the last 10 years is beyond me. Why even make a SATA-only SSD in the first place, rather than a SAS/SATA version - who knows?

️

 

[Samir]

Makes sense, but anyone actually tried it? I've got some sas drives and am wondering if they'll even power up.

And the reason is the same reason there were IDE drives when there was SCSI--people wanted 'cheap' so you have to give it to them. imo the lowest level sas drive is at the same level as the highest level sata--sas is just that much more superior. It would be interesting to see them run in desktop synologies--would be a game changer for sure for sourcing drives.

 

[Robbie]

No, not tried it or even contemplated it on my Ryzen 1500B SOC. The SOC design itself is only provisioned for SATA and PCIe with nothing for SAS.

I think you have a Celery J3455 SOC, a different vegetable for sure but I think it has similar I/O restrictions as the Ryzen.

️

 

[Samir]

I saw the sas sockets in my older ds214+ as well as a ds918+. I haven't check my others except I didn't notice it on my 213J and 215J so they probably don't have it.

 

[Dr_Frankenstein]

Recently dismantled my dying 1815+ ready for its re-incarnation, can confirm it also has a SAS backplane (well the ports are)

 

[Samir]

Very interesting. It would be interesting if there was a way to trace the sas lines and see if they're anything on the board for them.

 

[Robbie]

Looks like a SATA backplane with SAS connectors for the drives.

 

[Samir]

I can't tell what the traces look like from the picture, so I can't rule out SAS traces atm.

The only reason to perhaps use sas connectors as they may have a higher duty cycle for insertions/removals than sata ones and hence make more sense in something like a nas that will have more drive insertions/removals. Still, other companies and other products like multi-drive external enclosures don't do the same thing, so maybe that's a wrong guess.