More News From 10Gbit Land

Well, I bought the CRS317. Purchased from EuroDK for US$315 - best price I could find. Here’s a picture of it:

Brand new piece of hardware and I’ve opened it up already? Typical…

There was one tiny problem - something was rattling round inside. The light pipe for port #2 had come loose in transit.

Not hard to put it back in, but let’s see how it goes on our network…

So why’d I buy this? There’s three PCs, and a fileserver that I want connected together at faster-than-gigabit speed. The PCs shift large stuff from and to the fileserver and I’d actually like to get the third one booting off it, diskless.

The typical problem connectivity wise is that while switches with two 10Gbit ports are fairly easy to find, this provides little advantage if they’re being used to connect two hosts to the network, rather than a server uplinking to all the PCs. Four 10Gbit ports tend to be found only with 48 port gigabit switches in a large, power-hungry, noisy and expensive rackmount unit. (Quanta LB4m is reasonably common… loud and 60 watts idle)

16 ports is more than I need - but the CRS317 is still cheaper than pretty much everything else. It’s also a shallow depth rackmountable unit, and the decent passive cooling means that in normal conditions, the fans stay off (out of the box this wasn’t happening but works fine once upgraded to RouterOS v6.41rc52). You can also boot SwOS - a much simpler OS meant for switches - it has a lot less features but is a little simpler to configure, performs marginally better and boots faster.

Using RouterOS means it’s capable of doing routing - but be aware that any routing or other L3 features mean your packets go through the CPU. Performance will hence be limited to about 3Gbit/sec - but I don’t think you’ll see much better than that out of anything at this pricepoint.

One potential downside is that it only supports SFP+ 10Gbit ports, not the newer NBaseT / 10GbaseT standard. Fiberstore has SFP+ to NBaseT adaptors but they’re US$280 - and due to power limitations they’ll only do 2.5/5Gbit at 50m, or 10Gbit at 30m, instead of the 100m maximum. Mikrotik’s got the S+RJ10 at a much better price point of US$65, with the same 30m at 10gbit limit, however this one doesn’t seem to be in stock at any reseller yet…

If you don’t have a requirement to run over Cat6 copper cabling, the SFP+ gear is cheap. Mellanox ConnectX-2 cards are my personal favourite - they can be found for as low as US$40 a pair second hand. They don’t have as much offloading as newer cards but this isn’t as big a problem now if you have a reasonably fast machine.

Plans changed regarding where the switch is going to be mounted, so it’s now going with the fileserver, and I’ll use the two fibre runs to connect the two desktops. Another two of the Mellanox cards are still on the way, so I’ve still only got two machines connected. Right now, I’ve got a SFP to Gigabit adaptor connected to the CRS317 for uplink back to the Mikrotik hAP ac that’s our main router. You could use the front panel gigabit port but it’s not on the same switch, it goes through the CPU).

I’ve also got 1000BaseSX running over the other fibre to make use of the SFP cage in the hAP - but on that side it goes through the CPU, so at gigabit speeds hits 70% CPU. Both are connected, but STP prevents it from being a switching loop (and a higher port cost on the fibre side keeps it from being used). I’ll need to pick up a third pair of 10GbaseSR SFP+ modules later for the third PC, and put that one to a more productive use.

Here’s a more traditional view of the device. 16 SFP+ ports, one RJ45 ethernet and one RJ45 console.

Now, let’s attach the rackmount ears and put it into our “server rack”:

Configuration was pretty simple as it’s basically a switch - really just had to give the management interface an IP in our subnet, and reconfigure the two machines that were on 10Gbit to use DHCP again…

I’m considering having a separate routed subnet for the 10Gbit side to be able to use jumbo frames… with everything performance critical hanging off the CRS317.