Whether you deal with a couple of servers or a full cabinet of gear, organized cabling is important for numerous reasons. Some of you might be saying “no duh” at this point, but bear with me:
- Is your cabinet clean and organized when it comes to power and data cabling?
- Can you remove any device without the risk of impacting other connections?
- Does your cabling restrict the breathability of your servers?
- Is your setup intuitive and easy to maintain?
- If something failed in your setup, would it be easy to replace?
If you didn’t answer yes to all of those questions, there are a number of easy steps you can take to clean up after your cables.
1. Size up your equipment.
Review the physical styling of the equipment you have in your rack. Chances are good you can break it up into three styles: full-length devices, short-length devices, and switchgear. Group similarly sized items together, with space above and below for future additions.
2. Review your gear’s breathability.
This is especially important when considering your switchgear. Most data centers operate in a hot/cold row design. Almost all servers take cold air in from the front and exhaust hot air to the back. Switches, however, don’t always follow that rule, and if they do, you may be mounting them backwards to make them easier to cable up. Consider the following tips:
- Place like equipment together when it comes to the airflow for intake and exhaust.
- Do not leave 1U gaps between side-to-side airflow switches, as hot air can sneak back into the cold air intake (short cycling).
- Make sure passively cooled devices have a 1U air gap above them. This prevents them from dumping heat into actively cooled devices.
- Check with your suppliers to see if your switchgear has various airflow options that would work better in a cabinet setup.
3. Move power to one side.
If you use vertical power distribution strips, place them on one side of the cabinet. Look at the gear going into the cabinet and choose the side that the power supplies are on for the majority of devices. This gives you full separation between your power and copper cables to give you an easy way to manage the cabling.
4. Invest in custom-length cables.
No, I don’t mean you should go out and terminate every cable to length—just don’t use excessively long cables. The power and network cables that come with a server are designed to cover all environments. You might only need a cable that is three feet long, and if your cable is much longer than that you will waste space storing the slack. Ask your facility if they carry custom-length cables and in what sizes. If they don’t, there are many vendors on the Internet that provide data and power cabling in one-foot increments at a very reasonable price.
5. Stick to Velcro.
By far, this is the single most versatile cable management tool you can buy—and it doesn’t even eat up usable cabinet space. Most cabinets have cutouts for attaching Velcro to help tie down your cables. If you have a lot of cabling to do, make a large Velcro loop through which it’s easy to string cables, and then tighten it down when you are ready to leave the cabinet.
6. Strip away the excess.
Very few devices can actually be serviced live. If you don’t open your servers while they are powered on, you can probably get rid of those cable management arms to improve cabinet airflow. (Some storage arrays may use these arms for live serviceability, in which case you should look at installing service loops — neatly done coils of slack that can be undone — or, as a last resort, cable management arms.) The same approach can also be taken with front bezel covers. If you don’t need the functionality of the cover, consider removing it from your device.
7. Don’t cross over swappable parts if you can avoid it.
See if you can route your cables in a way that does not interfere with hot swappable parts. If there is no avoiding it, add enough slack to be able to shift the bundle of cables out of the way for service work.
8. Avoid waterfall cabling.
Route your cables 90 degrees across the device. Never let them hang off the back of the port. Hanging the cable can put a lot of stress on the network connection and could cause intermittent problems or equipment failure. By bringing the cables 90 degrees across the device, they can be bundled together to help provide support and they don’t interfere with other devices/open space above or below. This is one of the biggest mistakes we see on a daily basis and is easy to solve with a little Velcro.
9. Allow no more than 11 inches of slack.
If your cables come in one-foot increments, you should never have more than 11 inches of slack to deal with. If you do, swap the cable with the proper length. This process is a lot easier if you loosen the Velcro at the start of any cabling so you can quickly run cables through the bundle.
10. Color-code your cables.
If you have multiple switches and network connections, consider color-coding the cables to make it easier to tell which connections go where. This also helps when reconnecting a disconnected server, as you can match the pattern the other servers are using. If you do not have multiple switches, color-coding by purpose works too (e.g., one color for Internet connections, one color for internal networks, and one color for KVMs).
The results of clean cabling:
- Decreased maintenance window requirements: When cabling doesn’t cut across multiple devices or hot swappable parts, equipment is easier to service and maintenance time goes down. If you are paying for remote hands work, your operating cost decreases too.
- Less risk to other devices when work is performed in the cabinet: As data and power cables are segregated, tracing one device’s data cable doesn’t carry a risk of jiggling another device’s power cable. When cabling only cuts across the device that it connects to, you don’t have to worry about disconnecting something to remove or add a server.
- Decreased connectivity loss on other devices: Similar to above, when the data cabling has a common path and the bundles are tied together, they provide support to each other and help reduce connections from pulling out or bending outside of spec during maintenance.
- Less human error: When a cabinet has more open space, it’s much easier to understand. Better visibility means the risk of disconnecting the wrong item goes down. There is also the benefit of color-coding ensuring network or power connections don’t get reversed when reconnected.
- Less risk on 208V C13/C14 power connections: By far the biggest concern we have when working on a 208V C13/C14 cabinet is how much wiggle these connections have between the power strip and the power cord. By using Velcro, the cables support each other and are less likely to have a single connection wiggle free during maintenance.
- Less power usage and cooler equipment: By removing excess cabling and unblocking the backs of servers, cabinet airflow greatly improves. This means that the fans do not have to work as hard to push air past all of the blockages, and that cold air can flow more freely across the system. As the machines breathe better, their power saving features perform better, and you can see an actual drop in power usage across the entire cabinet. Not only will you be able to add additional gear, existing gear will run cooler and last longer. This is a huge benefit when you consider that power and space are the two most expensive variables in a data center.
After all of this work, your setup looks great and performs well. Now you need to keep it that way:
11. Train before granting access.
If you can, limit the number of people that have access to the cabinet and review with them the above best practices and how you implemented them. Explain the benefits and how keeping it that way improves their ability to work quickly and effectively in the cabinet. After they are familiar with how things are set up, have them show you their work for verification. This can be accomplished via video chat, pictures, email, or in person. Once they earn your trust, the verification step can be dropped.
12. Always keep extra cables in stock.
This tends to be one of the biggest reasons for people to do something wrong. They didn’t have the correct cable so they made a compromise and used the wrong cable. Keep this from happening by always keeping a basic stock of the common colors and lengths you use on hand. Again, check with the facility to see if they offer this and save yourself the hassle of having to manage it.
13. There’s no such thing as a temporary cable.
They do not exist, so do not let them happen. With a clean setup, it should only take slightly longer to do it right then it does to do it wrong. If you see a cable run poorly, fix it as soon as possible or it might become an example for others to do the same thing and take shortcuts.