> it's intended to be preterminated SFP-to-SFP

I wonder why nobody's making field-terminatable DACs for custom lengths. If you've torn one down, they're not exactly complicated inside.

If they existed, would people buy them?

Yes, thanks. It was confusing me for a second because no, no almost one is terminating twinax in the server room.

I had IT company recommend to me a bunch of fiber cables for a cleanup I was doing. They had about 20 or 30 laser modules we would need, and however much fiber.

When they asked why I planned on doing copper, I told him because each run is three fucking feet.

I’m not sure if they just didn’t realize that’s not what fiber is for or they didn’t know that DAC existed.

Pretty sure that's the copper they're talking about.

PCIe is also a full duplex connection so 2x10G is still just 20G instead of 40G. For PCIe 2.0 an x8 connection should get you full bandwidth on both ports simultaneously while x4 will fall just short for simultaneously usage (but still higher than 1 port). Unless you're really hankering for that full 20G, in which case a 25G NIC is definitely the better pick, that means you can just slot it in an x4 slot off the chipset on even a standard desktop PC.

Funnily enough, if you want a dirt cheap PCIe 3.0 based card the MCX353A-QCBT and MCX354A-QCBT give 1/2 ports of 40G QSFP+. They support QSFP+ to SFP+ adapters, so you can plug a 10G SFP+ into the QSFP+ port, but they don't support 4x10G breakout unfortunately. I ended up using the 2 port variant in both of my NASes - one port is 40G between the 2 for dirt cheap fast backups and the other is adapted to 10G to connect to the rest of the home network.

I've started buying Intel E810s for most purposes, even for 10G links. (SFP28 ports are generally backward-compatible with SFP+ DACs and transceivers.) The ones you can get on eBay for cheap typically run Dell firmware but it's serviceable. An E810-XXVDA2 is Gen4 x8; as long as the host slot can physically accept the card connector you only need Gen4 x1 electrical for a single 10G link or Gen4 x2 for dual 10G or single 25G.

I'm only planning on using one of the SFP+ ports on each of the cards, the dual port cards were just more common and cheaper on eBay.

The specs say they require PCIe v2.1 x8 lane.

My Proxmox server is quite old and has a Gigabyte GA-X79-UP4 mobo and has loads of spare PCI slots. One slot is taken up by a generic graphics card as the Mobo has no on-board graphics. (I think I went for this mobo because of the number of SATA ports, but it was over 10 years ago so not entirely sure.)

My general Linux server is newer and has an ASUS Prime H610M-A D4 mobo. Only two PCI slots (not used at the moment) and so the Intel X540-DA2 will use up the PCIe 4.0 x16 slot leaving just a PCIe 3.0 x1 slot. But that's fine as this machine is just a CPU (i7-13700), 64GB RAM and a 2TB NVMe. Sticking a good graphics card in it for GPU related fun had been on my list for years but I never got around to it, now the prices are just insane so I'll ignore that for now or something second hand falls into my lap.

My homelab has a 10G fabric (switched) for NFS, iSCSI, NVMe-OF, etc. and a 25G fabric (a mix of back-to-back and switched) for clustering (Ceph, DRDB, ZFS replication, migrating VMs).

I spun up some iSCSI-backed SQL Server a few months ago and 10G couldn't keep up with the workload, so I dropped in a pair of 100G ConnectX-4 cards with iSER (iSCSI Extensions for RDMA) support for that particular use-case.

Just because your uplink is less than 10G doesn't mean the rest of your network can't be a bit more capable. :)

True, I don't really feel limited by my existing 500Mbps down, but knowing I'll be having 2500Mbps up/down soon means I want to have the infra to handle it.

Basing things on 2.5GbE would certainly have been cheaper but some things don't support it (they either do 1GbE or 10G SFP+) so settling on 10G where possible made more sense to me. My future ISP also has a 5Gbps up/down option, but even I can't justify that right now.

My wife and kid just want their phones/laptops to work, and to be able to stream stuff to watch, they don't care about the underlying speed.

Having a faster network may make some of my work related things run a bit quicker. A few times a day I'll need to pull something big down (either an ISO or a bunch of docker images) and that can take up to 2 minutes with 500Mbps down. Having those take a fifth of that time will make it seem less of a roadblock to doing work. 2 minutes meant I went and got a cup of coffee and often got more distracted, 30 seconds should keep me at my desk and focused on what I was doing. That's not a big enough reason to justify it on its own obviously.

I also want to do offsite backups with/for various family members, so something better than 75Mbps up is going to be a huge boost. Getting 1Gbps+ out will be huge (assuming whatever is at the other end can support that).

I don't do any kind of data hoarding, I think I've got something under 4TB of data that I actually care about, and most of that are family photos/videos.

Deep down it's mostly because I'm a networking geek so it's fun to play with some new kit and make blinkenlights.

It's less "what new thing can you do" and more "what things involve noticeably waiting, how long is the waiting, and what else is impacted". E.g. updating a game on Steam practically takes slightly under half the time for me (1.2 Gbps actual rate) and has absolutely 0 impact to any other traffic in the house. If it was 10x the price to get 10x the bandwidth I wouldn't bother but it was actually about the same as my old cable modem plan.

For most people, 500M is probably fine. But once you have a few family members, each streaming 4K movies to their devices, and a parent that needs a video call to work seamlessly, you start to see the benefits.

10G is probably overkill, but it's also future proofing. The way things are going, loading the NYtimes will require 10G just for the advertising alone...

What if you want to access your NAS at 10g+ speed? You're focusing on WAN when there is also the LAN side.

I had a big debate with myself whether to go Mikrotik or Unifi. Being EU based I really wanted to go Mikrotik but ended up with Unifi as I'd had more experience of it when helping out friends/neighbours.

Maybe my "last house" (i.e. the one we'll get to see us through to retirement and beyond) will be Mikrotik based. By then I'll probably want as little computing stuff as possible and will just sit in a comfy chair doing crosswords and sudoku with a pencil.

Ha. I meant the rest of the equipment (USW-Aggregation, Unifi Pro Max 16, UNAS Pro, Unifi Express 7) was somewhere around half retail price.

I think I paid ~$15 for each X520-DA2 including postage.

The limiting factor for me is that I'm renting so I can't put my own cabling in to the property. And with the new place there's no existing cabling, nor any conduits to run anything in, and chasing things into the walls/etc is going to be prohibited by the landlord or just too expensive if I'm only in this place for a year or two.

The spools of bend insensitive fibre are pretty cheap and very discreet so I'll probably have a couple of those running along skirting boards/etc in order to connect disparate areas of the house. (The ONT is ~15m away from where the majority of the equipment will live, that's the main bit I have to bridge.)

I think DAC has to win out on price not because of the price of the fiber patch but those optical modules can cost some money.

I'm getting a really bad taste in my mouth for 10GBASE-T RJ45 SFP+ modules mostly due to the god awful heat they pump out (which scales linearly with power draw): So when we are forced to use them (for example to connect to a far end that only accepts 10GBASE-T) we often cannot use any SFP cage directly adjacent.

I had the Twisted Pair/DAC/Fiber discussion with one of my an engineer that we peer with recently and they made the pitch for Fiber that "being able to see the light levels takes a lot of the guesswork out of their troubleshooting". So I do have to admit that that is one utility lost when choosing a DAC over Fiber even in a rack, but my counter is that DAC has fewer moving parts and thus a lower surface area for failure in the first place.

We have had some gear refuse to work with some DACs (just as some gear refuses to work with some SFP+ modules of various stripes) but aside from that I have yet to see a DAC that starts working stop working, while I get that with fiber runs (though usually the longer ones running outdoors) quite frequently.

Couldn't have said it better myself.

> Nowadays I'm not actually sure if DACs are cheaper than fibre now

Yep still are, although fiber transceivers are surprisingly affordable, and of course you can usually re-use jumpers when you upgrade transceivers so TCO over a couple generations might be comparable.

Thick DAC cables, especially long ones, can be very resistant to cable management. Then theres the deal with trying to detangle it in the first place.

Huh, what were you doing, buying Cisco/HPE, or trying to use fancy single mode optics for distances that DACs could do?