Which copper SFP+ to pick for a DGS-1250-28X feeding a TerraMaster F4-424 Max NAS
Home setup, everything in one rack. I want to connect the NAS to the switch faster than gigabit, but I don't want to run fiber: the distance is about five meters, a plain patch cord covers it.
- D-Link DGS-1250-28X switch, SFP+ ports free
- TerraMaster F4-424 Max NAS, copper RJ-45 port
- short Cat6a patch cord
- SFP+ RJ-45 module - this is exactly what I'm choosing
The price spread is confusing: suppliers list modules with identical descriptions priced several times apart. In the switch's own datasheet exactly one copper module is listed:
DEM-410T - D-Link, 10GBASE-T SFP+, listed in the switch documentation
"10GBASE-T SFP+" - noname, specs match line for line, several times cheaperWhat I've already done:
- read the switch datasheet, found DEM-410T listed there
- asked two suppliers about the noname module, they say "should work", won't confirm it in writing
- searched for independent compatibility lists for the DGS-1250, found nothing concrete
Is it worth paying extra for the genuine DEM-410T, or will any copper 10GBASE-T module go into this cage? And what should I actually be looking at beyond the "10GBASE-T" line in the description?
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Comments 2
The boring answer to "what to get" is: get what the vendor itself lists in the documentation for this switch, i.e. the DEM-410T. Bargaining for a noname only makes sense under one condition - the supplier confirms compatibility with this exact DGS-1250-28X in writing and accepts a return if the module doesn't come up. A verbal "should work" is worth nothing.
But check something else before buying, otherwise choosing the module isn't even the right question. The F4-424 Max port isn't 10 Gbit/s, it's 2.5. That means you don't just need a 10GBASE-T module, you need one that negotiates down to 2.5G, and the D-Link SFP+ cage has to accept that mode. Copper modules with 2.5G/5G are exotic, usually not on compatibility lists at all, and the link on them either comes up at gigabit or doesn't come up at all.
One more general point about 10GBASE-T in SFP+: such modules are limited by power budget and line length. One person with about 15 meters of Cat6a had the link stubbornly come up as 5000Base-T, and when 10GBASE-T was forced, throughput dropped to around 100 MB/s. At your five meters that shouldn't happen, but keep in mind that copper SFP+ is always a compromise.
So first pin down the speed class on both ends, and only then pick the module.
I'll add something about locking the speed, since 2.5G came up. In my CRS305's SFP+ cage there's a gigabit copper 10Gtek - not SFP+, but a plain 1G RJ-45. Under SwOS 2.18 it works fine and doesn't get hot, but with one condition: autonegotiation has to be turned off on the port. As long as autonegotiation is on, the link simply doesn't settle - the cage is ten-gig, the module is gigabit, and they don't agree with each other.
What this means: if you get a module of a lower class than the cage, plan on having to pin the speed by hand on the switch port rather than relying on autonegotiation. And if you do end up going for honest 10G over a long patch, look for modules with power headroom, like the MikroTik S+RJ10, cheaper ones usually fare worse there.