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The amount of time required to terminate a copper cable in the field is seconds, and felt a bit like art. Something about the way it reliably reacted was magical and felt "strong."
Terminating or splicing a fibre cable felt like wrestling a snake covered in melted crayons, and the failure rate was significantly higher across the board. And it wasn't just workmanship, but quality of product, terminating environment, available equipment, misuse by future operators etc.
That said, at a certain point, we as a firm learned that most purchasers would rather the low latency/small footprint of optical/fibre versus copper, maintenece/failure be damned. Though, maybe part of our willingness to push fibre came from knowing that most purchasers would in 1-2 years call us back in to replace the rack terminations with copper :)
First there is the BASE-T RJ45 stuff, which it sounds like you might have been working with. At 10G or higher speeds this get relatively power hungry and is not really an advantage over fiber unless you are also delivering PoE or are trying to reuse existing cabling.
This type (DAC) is a special type of pre-made cable assembly which eschews much of the advanced signalling/conversion logic. The upside is the power usage is low (often even lower than fiber) and the cost is dirt cheap. The downside is the lengths are much more limited and it's intended to be preterminated SFP-to-SFP (or the like) cable assemblies instead of modular patching/custom built.
There is indeed a latency difference, usually DAC < fiber < BASE-T, but they are all within a few microseconds (not milliseconds) of each other so you really have to be pressed to care about it (to the point you're looking at specialized low latency switches and paying extra to lay things out in a way which minimizes the number of L2 hops rather than the cost).
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?
DAC cables have a limited length range. It's not like 10GBASE-T where you can run the cable hundreds of feet and then put a connector on exactly where you need it. The cables only work at short distances so it's easy to stock the cable sizes close enough to everyone's needs.
For passive DACs the range of lengths is so low you can just get away with having 2 or 3 different lengths on hand and never need to worry about it. Active DACs start to be too much to bother with again.
Fiber it's possible, but again really only because you can go kilometers with it rather than because people want to make short patch cables themselves.
This article is about Direct Attach Copper (DAC) cables which are not something you can field terminate. They use twinax copper and have special modules on the end.
You are thinking about standard RJ45 terminated cabling for 1GBASE-T or 10GBASE-T, which is a different.
> That said, at a certain point, we as a firm learned that most purchasers would rather the low latency/small footprint of optical/fibre versus copper, maintenece/failure be damned.
Direct Attach Copper has slightly lower latency than fiber, but the difference is negligible. Both have significantly better latency than 10GBASE-T through twisted pair cabling.
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.
1. The copper cables discussed in the article are not field terminable. And if they were, they'd be a pain in the ass.
2. Terminating fiber used to be a pain, but is now pretty easy with the right tools, fuser, and someone with basic training. Even cheap fusers do the job with very low failure rates. They now have so-called "knuckle draggers" terminating fiber.
Copper bundles get real thick, real fast: I ran an OneFS cluster for many years, and we had >50 nodes, and all the cables (each node dual-connected) ran to two central switches for backend replications. Rat's nest.
I was very happy when Isilon started officially supporting active optical cable (AOC) on the backend. Really helped with airflow and keeping things tidy.
I have never heard of the possibility to field-assemble DAC cables. Usually that's when you switch to fiber
https://kohlschuetter.github.io/blog/posts/2026/03/22/unlock...
I have a USW-Aggregation with 8 SFP+ ports arriving today too. Just have to install Intel X520-DA2 cards in two of my servers (Proxmox host and a general Linux server), and the NAS also has a 10G SFP+ port, and then connect it all up.
Most of it second hand from eBay for half the usual retail price.
I went with some cheap eBay cards and slotted them into a synology and PC.
They work great and have for years.
https://www.ebay.com/itm/384094168784?_skw=connectx+mellanox...
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. :)
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.
One thing to remember is 2.5 gbit/sec uplink is shared between all clients. So if one client is on 1 gbit, and one client could saturate their 1 gbit while switch and router can handle better. An advantage of that is QoS isn't needed to be applied manually.
So, for example, it maybe worth it to have higher than 1 gbit uplink on switch to router, and maybe a server to switch, but devices such as your TV or WLAN clients do not need such.
75 mbit up is pretty good compared to DSL (I bet it is cable), and yes 1 gbit up is nice for off-site backups. But the upsell of going above 1 gbit symmetric IMO isn't there.
Cable providers know this. Which is why they sit below 1 gbit symmetric, at a level average subscribers are comfortable with.
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...
You must have a very large family. To saturate 500Mbit/s, you'd need around 30 family members all streaming at the same time.
The card is obviously 16-lane, but it also has two ports; 40Gb total. In a server that’s fine, but if you want 10G in a desktop you’ll have a problem.
I’m probably not telling you anything new. NICs using newer PCI generations are rare as hen’s teeth. It should be possible to do this with four lanes, but isn’t…
Unless you find a 25G dual-port card, in which case the single lane my secondary slots hand out does at least suffice for 10G one way.
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.
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.
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.
And even if you're a bit scared of manual configurations, the web GUI and Claude understand it pretty well.
It's documented (but -IMO- poorly) that the default username is "admin" and the default password is the empty string. The brand-new-as-of-today docs site is at [1], the "older" docs site is at [2], and -as documented on the older docs site- you can get a PDF of the docs at [3].
If you ever find yourself with an entirely spare hour or two, fire up the VM just to play around with the interactive shell that they have built. I may not have worked with enough Enterprise Devices to have an informed opinion... but once I understood what the shell was telling me, I found its use of color to be helpful both when attempting to learn the basic syntax of the shell and as a reminder of what tokens are valid in which contexts. I've never worked with another interactive shell that has such nice syntax-and-data validity hinting.
[0] <https://mikrotik.com/download?architecture=x86>
[1] <https://manual.mikrotik.com/docs/introduction>
[2] <https://help.mikrotik.com/docs/>
[3] <https://box.mikrotik.com/d/df76f0d495284eb1b6a1/>
You were scammed. X520 is old enough to drive a car, the shop should pay you to get it off their hands.
I think I paid ~$15 for each X520-DA2 including postage.
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.)
For the benefit of other folks reading, I'll note that even regular, boring OM4 bends okay. I have mine running along the outside of preexisting molding and baseboards. My runs get down to a 1/4" bend radius in places and it seems to work just fine. Bend-insensitive fiber is definitely useful, but it may not be required for the run one is planning.
Though, one thing that regular OM4 is not is discreet. That two-strand cabling in its aqua-colored jacket is quite distinctive.
This vid comes to mind when you said bend insensitive fiber: https://www.youtube.com/watch?v=Z2FbzCyiNr4
Yes on an absolute sense, DAC can be cheaper, but for a homelab or something, it’s not that much different. Also, it’s much cooler to run fiber optic to things (imho).
DACs will usually be even (slightly) lower power per port, and slightly lower latency[1] (we’re fighting over microseconds here!), with excellent durability. The tradeoff is for passive DACs you’re limited on range, cost is often higher, and they may need to be encoded for your interfaces. Moreover, the range is very limited.
Fiber (the cable) is immune to electrical noise, can run long distances, advances in wave division multiplexing extends the life of the fiber by changing what’s the fiber connects to. The downside is you pay slightly in latency for media interface changes (the electrical-to-optical conversions), the limits of bend radius of the cable to not break the cable or reduce bandwidth, and the relative complexity of field terminations compared to twisted pair. I’ve 25+ years experience with fiber, and trust me, it’s great.
————
Outside of cost, both crush twisted pair like an ant. The power consumption per port is also far lower. However, this is only going to matter if you focus on limiting power consumption (not for cost, on principle), have very high-bandwidth applications where latency matters (I do!), and/or just want field experience with things other than twisted pair.
I use DAC and fiber for some things as I try to get every scrap of capability out of my hardware. For example, I have VERY low power (silent or near silent) hardware where I can push 5GB (so ~40Gbps) / sec storage. Not just sending it over the wire, but actually committing it to disk without buffering in RAM. So I have the capability of “PCIe 3.0/4.0 x4 NVMe” speeds across the network… from the (mostly silent) storage server, to anything else that can send or ingest the data that fast. Despite the storage server having very little flash (a few TB vs 100TB+ disk). That’s harder to do with twisted pair, or at least the power consumption of the network connectivity itself starts to add up for a few virtualization cluster nodes.
———-
Generally, “DAC in the rack, fiber to out back” is a reasonable approach. Though “fiber-only” works if you want to limit complexity!
[1] Fiber and DAC tend to trade places on latency every generation or so. It’s a very close race, but they crush twisted pair.
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.
It's truly bananas especially in a homelab environment. Nearly every time I've thought to myself "oh I can just do a copper gbic for this" it's been the wrong thing to do.
However that was mainly because I always thought fibre was much more fragile. I mean in a sense it is, it really doesn't like being pull through a thatch of other wires. The solution of course is to do nice cabling.
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.
This is generally good enough for intra-rack runs, especially if you put your top-of-rack (ToR) switch in the middle: you basically only have to go about 1m/3' in either direction (up/down).
We have OSFP/QSFPDD with 8 lanes and lane speeds of 100Gpbs and 200Gbps for up to 1.6Tbps on a single DAC at the bleeding edge. Although with these signal integrity limits the maximum length to about 1m.
You probably won't see this on a NIC or anything for home use any time soon though.
There is also a new generation of "invisible" fiber that is interesting for home use. Basically looks like fishing line so you can run it somewhere that you just don't see unless you're really looking. Fragile tho
You make sure all of the cabling has ends that can be pulled safely through the rat nests in the ladders (EG especially RJ45 cabling needs competent clip guards) and Bob's your uncle
Downside the cables are kind of heavy and sometimes folks dont like that.