I thought this would be something simple to search up but apparently not. I’m looking to order some DACs to connect 7 switches within a rack. There’s a 2U 48 port patch panel between each switch. I want to avoid cables that are too long. What is the proper length of a DAC (total length including tranceiver) to cover a 3U distance so I can have a clean efficient rack? Is 0.3m too short? 0.5m too long?
Thanks
What Switch, and what bandwidth?
5x Unifi Pro’s (SFP+), 2x Datto DNS-E48’s (SFP)
Rack will be setup in the following orientation:
1U 24 port patch panel
1U 48 port switch
2U 48 port patch panel
1U 48 port switch
2U 48 port patch panel
1U 48 port switch
2U 48 port patch panel
1U 48 port switch
2U 48 port patch panel
1U 48 port switch
2U 48 port patch panel
1U 48 port switch
2U 48 port patch panel
1U 48 port switch
1U 24 port patch panel
I was hoping to get rid of the Datto Switches for one with 10gig uplinks but that isn’t going to happen.
Are you doing an aggregating switch, or just jumping from one to the next?
Just one to the next. Nothing too fancy, just SMB stuff.
To travel 3 rack units distance if both SFP ports are on the same end of the switch, then a 0.3m cable will be good.
You can also get SFP transceivers with LC connections on them and use fiber cable. It is likely more expensive, but you can use 1ft fiber and make a small loop in it and use a twist tie to hold it together. Looks a lot nicer organization-wise (not color-wise) and is thinner than dac cales.
The DAC cables will be an order of magnitude cheaper and produce significantly less heat and consume less energy.
These should do it.
Or if you want to pay a bit more but get nearly the same cable with Ubiquiti name on it:
NOTHING should ever go vertically across the front or rear of a rack. EVERYTHING should go horizontally into the vertical wire management, up or down within that channel, then out next to the device where it needs to be connected. Assuming you’ve got halfway decent vertical wire management that has a finger every 1U and lots of open space for up to 50 cables each, that gives you an incredibly clean and imminently manageable rack, with nothing interfering with accessing, servicing or removing equipment, you never need horizontal wire management which wastes space in your rack, and it’ll scale up or down nicely from the simplest most well managed rack, to the most hectic/dense/frequently ad-hoc altered rack.
With that, 1m is the bare minimum, but you’ve got lots of room in your vertical wire manager and don’t need to worry about the difference of 0.2m of slack for a cable. So 5ft/1.5m is the shortest I ever get, which is a nice length that covers most nearby connections including server wire management arms. While 7ft/2m is also a convenient size that will connect things up to half a rack away.
Thanks for the advice. I’ll take that to heart. One reason I’m still tempted to wire things vertically is due to everything in the rack being directly beside what it’s connecting to. There is nothing but patch panels and switches in this rack. All other infrastructure is going to other racks, so I’m in the unusual position of being able to run 6" patch cables between each switch and it’s neighboring patch panels.
As far as the trunk lines between switches originally I was going to daisy chain them from top to bottom. However upon reflection I’m assuming it’s better design to have them branch off each other in a binary tree type configuration in case one switch fails it takes down less downstream switches. I don’t have any core or aggregate switches. If this is the case I’ll likely keep my 6" patch cables going vertical and then run longer DACs horizontally and through the cable management.
Right, I’ve seen plenty of racks start out that way. Then one octet of ports on a switch fails, and you need to run some longer cables to a different switch further away. But now, you’re running these new cables horizontally, under/over/through these existing short vertical cables that are sticking several inches further out the front. It looks like garbage, it makes it more difficult to run cables in that area later, you don’t have any slack to move your switch/patch panel around a few inches without disconnecting all the cabling on the rare occasions you need to fix one of the patch punch-downs, or make a few inches to maneuver some neighboring equipment-in.
Not criticizing you, specifically here. You may be in a circumstance where taking a section of your network offline for a couple hours on zero notice is always easy and convenient, you have plenty of free time to re-do the wiring of parts of your rack when the situation changes, and the price from the shorter cables may add-up to significant enough savings for you. I supposed I’ve just got data center PTSD from all the intractable messes I’ve inherited and had to spend so much time fixing, that so easily could have been done right in the first place. If only every High School and College level computer course spent a few minutes on rack wiring.
