Totally enjoyable video, funny and educational all in one, well done!!!

Totally agree Morten. Fiber is good for distance, but not always practical or cost effective for short distances. Copper still work very well.

Very good video, even though I disagree! In the data center, if you have 20 or 30 connections in a rack - even just to the top of the rack - the cables of DACs quickly become very difficult to manage. Fiber, on the other hand, takes up very little room, is more flexible, and is much much easier to pull to another rack (no need to push and pull an SFP through the tray). And, at least for us, dirty fiber/SFPs isn't an issue as the covers only come off the second before it's inserted, and fiber is never reused. As single mode fiber and optics have gotten cheaper, we've moved to a "Single Mode Everywhere" design. For 10G we use LRM transceivers (as opposed to SR or LR) to limit the costs and the power use, and they have the added benefit of working with single mode or multimode in case we are forced to use MMF due to legacy equipment. I'm not completely opposed to using DACs (and you make some good points), but I'd prefer to use fiber any day.

Another advantage of DAC cables is low power consumption (arround 0.3 Watts at each end), however length of DAC is limited to 7m. That's the reason, why I am using an AOC cable (power consumption arround 1 Watt at each end) to connect two switches at different rooms at my home, all other connections are either connected using DAC or 2.5 Gb SFP+ RJ45 transceivers or 8x2.5Gb + 10Gb SFP+ switches. Meanwhile these kind of switches became cheaper, If you buy them at Aliexpress. Regarding DAC and AOC resellers, I totally agree FS provides good quality, no issues.

Since upgrading to 10gbe both home and shop, we went all dacs. so easy and simple.

I worked in a few datacenters, no top of rack switches in the older ones, only the newest one had them. DAC was used to connect the NetApp Racks to each other and then fiber to the switches

We've used AOCs instead of DACs in our datacenter, mostly to ensure the lowest latency possible while avoiding the issues around LC and other connectors.

DAC == Direct Attached Copper. DAC started out with all-copper but you can actually find fiber DAC cables. Which seems weird but it works. My assumption is it uses low-power lasers vs. MM/SM transceivers. Enjoyed your video! A lot of people use SFP/SFP+/QSFP+ at home for their labs. I couldn't get by without DACs because the cost is so small compared to fiber or RJ45 transceivers.

100% agree fiber for long runs greater than 200M - thanks for another great video!

DAC Cables are very nice. We are using 3 of them in our two racks, for 2 Proxmox Hosts and one (now) in spare for a TrueNAS in the future. At home I use fiber, but I had to go through my whole appartment, so DAC is a little bit short and to thick...

Definitely love the convenience of DAC cables.

For my DC... We have a bin of a 10G DAC cables... But a lot of our servers go 25G now.... My company stock AOC (Active Optical Cable), it's a cable (fibre + 2 transceivers hard wired), and it's nice to manage yes, but one faulty wire... Left a bad experience for me, much rather regular DAC copper cables 😂

In the rack, I prefer fiber interconnects between equipment I want electrically isolated - that way if one of my outdoor security cameras happens to pick up a surge from lightning, only the devices electrically wired to that particular switch would be potentially exposed. You'd be surprised at how easy it is for lighting to induce a charge on an ethernet cable.

We do use Direct Attached Copper to interconnect switches with LAG.

I like DACs for short distances in the same rack. I use Digitus and they work in all servers and switches i have. As GBICs I use TP-Link. 10gbit cost about 30€ and work perfectly in DL380. All fiber-cables and gbics are way cheaper than years ago. But switches with more than 4 sfp+ ports are still expensive. I have one 16 port sfp+ and hope it will never get damaged because it was really expensive (~3000€ at the time of purchase). And now switches with that many ports are hard to find and often not available.

I use dual port 10 gigabit SFP+ NICs with DAC in my home network to connect my workstation to my server. Works great for iSCSI/NFS/CIFS and internet connectivity. It was actually quite a bit cheaper than buying 10 gigabit RJ45 ethernet NICs. I had to force the driver to install on Windows 10 on my workstation. The installer refused to want to install on anything other than Windows Server.

For me, the two biggest deciding factors as to what type of cable I will use is length and price. DACs are shorter and cheaper, whereas fibre are longer and more expensive. I use, I think it's 15 cm SFP+ 10 Gbps DACs to go between my NAS systems (which have been decommissioned). And then I have four 1 m QSFP28 100 Gbps DACs for my compute nodes to go to my Mellanox 100 Gbps switch. And then I think I have to 100 m long AOC cables, one of which goes to my system which runs the LTO-8 tape drive, and the other used to go to my micro HPC cluster headnode, but now goes to the second port on my consolidated server. (Yes, I run 100 Gbps Infiniband in my basement.)

There is also a reduction of latency in the DAC as there is no conversion with takes time. I believe FS has an article on their site with test results of fiber vs. copper.

Done a bit of service work, and agree that DAC is really handy for top-of-rack connections *unless* your server needs to be extended regularly with the DACs remaining connected via articulated cable management arms - such as top-loading dense storage servers like the Gen8/Gen9 HPE 45xx, designed to stay online during disk swaps. In such cases, you can get bend radius right with fibre and not have to worry much after that, but I've seen what looked like copper DAC cables reaching fatigue/work hardening failure from regular disk changes on top load servers. (aside: Pretty sure I was the first, and also possibly the last guy who ever had to install 2*IB + 3*Cat5 + 16*12G SAS cables through the HPE Gen9 4520 cable management arm, to allow online disk changes in the 4520 chassis while the 2 server blades stayed connected to 2 multipathed/multihomed JBOD chains; HPE Lustre Scalable Storage was *only barely* that scalable. My pictures of what I made work went in the installation guide, and were... daunting.) Anyway - I've seen instances where arm extend/retract cycles and challenge of keeping strain off the DAC SFP connectors when such servers were fully extended led to intermittent network failures - making the disk replacement hazard window more hazardous, and leading to "complicated" service cases that made life great for the field engineers. :^\

I do agree to your point of maintainability, but you also get more flexibility with fiber cables. In my case, the switch is 24x25Gbps+2x100Gbps ports, the fiber cables allow up to 100Gbps, the SFPs I got were 25Gbps SFP28 from FS, and the NICs are all 10Gbps (SFP+), the 25Gbps NICs are still around 250€ each and for 4 servers is quite an investment, so the plan is to keep as much as I can 25Gbps capable and replace the NICs to 25Gbps when prices lower a bit more. I do understand your point about the DAC cables, but you lose a bit of flexibility it really depends you your specific case and how often you're going to change things.

I must say, I do like me some Infiniband 40Gb copper 😎 QSFP+

I work in a datacenter as a security guard and I keep on encountering discarded LC cables, UTP cables and DAC cables(!) in the e-waste container. So far I am still unsuccessful in explaining why companies would throw away their valuable DAC cables!? Sure, they might not match the length requirements of new builds; but DAC cables do not break as easily as LC cables. In addition to this; DAC cables are rare and more expensive than ANY type of UTP cable. Do you know any scenario in which DAC cables which seem undamaged are better thrown away as e-waste?!

And.. it's faster.. Yes DAC has lower latency then fiber. Because in fiber needs to be converted to light. and the other end needs to be converted back, which is causing more latency.

DAC all the way ideal solution if you stay within the same cabinet, Or to cross connect two node / server HCI solution without a very expensive switch. And if there is something wrong it's easy to diagnose by replacing the cable,

Power usage has become a hot topic these days. Can you do a power draw comparison between fiber (sfp modules) and dac? This would highlight how much power you can save with dac cables instead of using fiber

Say I have a home with 5 PCs and 9 POE cameras, and a few other ethernet devices for smart home, like a Hue hub, SmartThings hub, etc. The cameras are on a different VLAN, and the PCs contain some VMs that are on their own VLAN, running little web servers. I am interested in the PCs having 10GB connections to a switch, but don't need more than 100mbps for the cameras. Should I use multiple switches for this? I don't know how I could get a managed switch that has PoE ports for the cameras but faster ports for the computers. The maximum distance between computer and switch is about 15 meters and I can easily run a new type of cable, be it DAC, Cat6, etc. Do you have any suggestions?

Cable managing more than a dozen DACs in the same rack quickly becomes a problem since the cables are thicker and you cannot adjust the length of each cable by redoing the plugs like RJ45/BNC/others. Fiber optics, although has to be deal with care they are much thinner and easier to cable manage when the number of cables becomes a problem.

I don't know about you Morten, but i've already switched to 100Gb ethernet network and fiber is the way to go :) DACs -> thick, limited to 1-3m, expensive (!)

The 10Gbe transceivers get dangerously hot. Mine are currently at 85 degrees celsius. They will burn you.

Thank you! I have an unusual case, I want to make a small board that connects 2 DAC passive cables at 100GB speed. But I can't get the host system to work through my board and 2 DAC passive cables. The DAC cable is 50cm long. The lines on the board are 15 cm long; there is an overlap of RX TX signals on the board. Tell me where to look? Who did something like this?

Cool haircut!

Is this preferred over 10GBASE-T? (when using 10 Gbps, obviously)

have any luck rebuilding raid 50 arrays. ? I have a equallogic ps4100 that needs love, can you help?

Agreed

Same split - longer runs, fiber (noting the correct quality is needed as using 1G fiber to run 10G links is temperamental) and for the short ones, DAC. I have some very short 10G DAC runs that I believe are 30cm or 25cm long, through to about 2.5m. The SPF(+) compatibility can be a royal pain in the @ss

This is likely a non-issue for most people, but no one else mentioned it. The DAC cables have 3X the latency of the fiber connections. We're talking about 0.3NS VS 0.1NS, but if your system uses lots of small packets, this would be relevant.

Morten sir, the SFP's and fiber "they use power" they use less power than old rj45

DACs are fantastic but as you said a lot bigger than fiber... can get bulky pretty easily if you have lots of connections to make 😅 And FS dacs are still on the thin side, Juniper or Arista 10-25G we use at work are a huge PITA, thick, hard to bend and if you ever need to remove one from a bundle in a cable organizer good luck 😂they stick together like glue!

I wonder if there's any difference in latency between DAC and Fiber because of the additional electric->optical->electric conversion. Anyone having any real info on that?

👍wow great I can't afford fiber yet

Why not just use cat6 for 10gbit?

i use only dac cable

Look at this guy... Imagine not having spare satellites to jump connections around. Couldn't be me :p On a more serious note... Yes please don't use fiber on the actual rack...please use DACs. Make life for everyone easier please. So you can get the QSFP in fiber. It is called MTP (multi termination push-on) fiber. Which uses MTO (multi termination optic). So one side is a MTP and 4 LC

Why not AOC?

I borrowed a new house from my grandparents, the story repeats

Funny, you just answered my question in my head of last days. I was checking 10Gbit options for my Rack with NAS and Hyper-V HPE server stuff and was thinking about Mikrotik 10Gb switch and if i can connect via DAC cable as i found Mikrotik DAC so cheaper in comparison with SFP+ modules + cable itself, Fibre or RJ45. And i just did not understand, why the hell is that so cheaper, i was not sure, if it would even work, or if DAC is just some connection only between switches itself.