Synology DS1821+ SFP Networking

[DocMadCow]

I just picked up a Synology DS1821+ as I needed more bays and my old DS920+ only supported faster network speeds via USB with unofficial code. According to reddit the Mellanox MCX311A-XCAT network card is compatible which has an SFP port. Until now I've only used 1Gbe and 2.5Gbe Base T and so I had a couple questions. Firstly with these cheap switches that keep being reviewed with an SFP port can I just buy one of these cards bundled with a double ended SFP connector like this ebay listing and plug it into the SFP port? Secondly are there any compatibility issues with SFP connectors between manufacturers or is it a fairly generic standard?

 

[blunden]

Firstly with these cheap switches that keep being reviewed with an SFP port can I just buy one of these cards bundled with a double ended SFP connector like this ebay listing and plug it into the SFP port?

Those cheap switches don't use any vendor locking so they generally work with all SFP+ transceivers, although not necessarily with passive DAC cables. Mellanox ConnectX-3 network cards like the one you mentioned generally don't have vendor locking either.

What you see in that listing is not a cable with SFP+ "connectors" at each end, it's a multi-mode fiber cable (OM3 or OM4 based on the color) plugged in to a fiber transceiver at each end. That combination should work fine with all these cheap switches.

EDIT: I see that the other pictures show that it's indeed an OM3 cable with LC connectors on it, which is very common. While I've never heard of the CTvbs brand before, they possibly just rebrand transceivers from someone else.

Something i find kind of funny is how they can't decide whether the card is made in China or in Israel. It varies in the different pictures.

Secondly are there any compatibility issues with SFP connectors between manufacturers or is it a fairly generic standard?

Compatibility is generally very good, but enterprise switch vendors and NIC vendors tend to implement artificial compatibility issues through the use of vendor locking. Basically, they want you to buy their overpriced transceivers so they don't link up if the transceiver doesn't have their vendor code etc. programmed in its EEPROM. That's why there are multiple companies that pre-program transceivers to work with the enterprise vendor of your choice.

Vendors like MikroTik and Ubiquiti don't implement vendor locking though. Also, Intel NICs can generally be unlocked. Many of the enterprise switch vendors also often have commands to disable the lock.

 

[tsteine]

I've had a mellanox connectx-3 40gbe adapter in my DS 1821+, they work fine, and runs the same driver as the 10GBE variant, though I tested it on version 6.2, I've not tested it on DSM 7, since the connectx3 was repurposed for something else, and it's now running an intel X710-DA2. Though MLX4 inbox drivers are still part of the linux kernel, so I think its a pretty safe bet that it'll still work.

As for transceivers, Mellanox cards will eat just about anything you throw at them so no worries there.

 

[Karpo]

I think easiest and cheapest solution is to use DAC cable like: https://www.amazon.com/ipolex-0-5-Meter-SFP-H10GB-CU0-5M-Ubiquiti-Supermicro/dp/B06XNRLWCQ

Fiber is good if you have more distance to cover like over 10f