Storm warning: When lightning takes out your datacenter

They say that lightning doesn’t strike twice in the same place — but a datacenter is a pretty big target.

Obviously, making sure all your electrical power work and grounding are done properly and sufficiently is your first line of defense for protecting your datacenter against lightning strikes. (As for protecting your datacenter in cold weather, check out our tips here.) If all your network uses fiber-optic cabling, then that’s one less thing you can worry about. But many datacenters still have significant amounts of Cat5e or Cat6 Ethernet cabling deployed both inside and outside the premises. And it’s the Ethernet running outside your building that can pose a threat in the event of lightning striking on your building grounds. Some of this outside Ethernet cabling may be used to provide connectivity with power-over-Ethernet (PoE) cameras for video surveillance protection. Other cabling may connect to WiFi access points stationed around your property. Is there a way you can safeguard Ethernet hardware from sudden high-voltage electrical surges that can damage them?

datacenter lightning

Have spare parts — before a datacenter is hit by lightning

For the outdoor stuff like PoE cameras and access points you have deployed around your property, you should start by making sure you have proper isolation in place. Dedicated circuits are the key here. For example, you should use dedicated power distribution units (PDUs) instead of rack PDUs to power any PoE devices you have deployed either inside and outside your datacenter. These PDUs should include built-in surge protection, and if they don’t, then make sure you have line-interactive uninterrupted power supply (UPS) units connected to them and not just standby UPS units. In addition, the PoE devices outside your building should connect to dedicated PoE switches, which should themselves then connect to your aggregation or core switches using only fiber-optic cabling.

You should also make sure that whatever you’re using to mount outside Ethernet hardware is also properly grounded. For example, if you have a PoE mounted on a tower, make sure the tower itself is grounded. An access point deployed in a shed or hut somewhere on your grounds means the shed or hut also needs to be grounded, including the gatehouse where your security person is busy playing Call of Duty when no one is around. Since these structures are likely standing on concrete, this is something that can easily be overlooked. Any passive PoE injectors you are using should also be grounded.

Since some hardware in your datacenter usually fails when a large electrical surge occurs, such as one triggered by a lightning strike, it’s also a very good idea to keep lots of spare parts around. This should include spare UPS units, PDUs, switches, and whatever Ethernet devices you have deployed outside your securely grounded building. And when it comes to such spares, make sure they are cold spares, not ones (not connected to electrical power), and that they are stored in a place that is easily accessible in the case of an emergency. And remember to note that there can also be potential differences between different grounding systems used in your building and surrounding grounds — see the chapters on grounding in this PDF for some good recommendations. And don’t forget that you need to replace any grounding rods you’ve sunk into the ground should a lightning strike occur and utilize them.

Cable considerations

Another thing to consider if you’re using Cat5e or Cat6 cabling is the specific kind of cabling you’re using. Ethernet cabling runs outside your building shouldn’t be done using the kind of cabling you can pick up from Best Buy, Amazon, or other Internet tech retailers. You need something much more resilient. For example, if you have Ubiquity access points deployed outside your building, consider using TOUGHCable, which is their outdoor carrier-class shielded Ethernet cable. You can find the specifications here in this PDF datasheet. Ubiquity also has Ethernet surge protectors specially designed for PoE devices, and you can use them to protect your outside Ethernet gear from power surges and electrostatic discharges — see their PDF datasheet here. One colleague also recommends these PoE inserters from MTC which provide Ethernet protection and surge suppression on the wire. The RBFTC11 fiber to copper converter from MikroTik is also good for outdoor use as it comes in a waterproof case with a PoE injector and power supply.

And for what it’s worth, you can also find Ethernet surge protectors on Amazon, though I haven’t tried any and haven’t gotten any recommendations either pro or con from my colleagues concerning them. And there’s also the question of whether any of these surge protectors are actually any use against a direct lightning strike on something connected to them. So, as they say, your mileage may vary in this department. And in any case, most of the time, it’s a strike that happens nearby, not a direct hit which can end up doing something like this.

While TOUGHCable is weatherproofed to perform well even in harsh environments, if you’re going to bury your outside Ethernet cable runs, then you probably want to go with something that’s more water-resistant — and, of course, more expensive. One colleague recommends direct burial shielded solid copper and gel-filled Cat6 cabling produced by Primus Cable — you can download the spec sheet here. This stuff is terrific in a storm or even a flood, but I’ve heard that it can be quite difficult to terminate as the diameter of the cable exceeds what your usual crimp-on RJ-45 ends can use. That’s a good reminder, of course, to always make sure when you mix and match hardware from different vendors that not only will they all connect together properly, but that the tools you usually use will also work with all of them. Another good shielded outdoor cabling some of my colleagues recommend are those available from Shireen.

Finally, you should probably balance the cost of replacing lightning-damaged Ethernet equipment vs. spending big bucks on deploying carrier-class gear outside your datacenter building. Use decent gear, take as many good and reasonable precautions as you can, and don’t hide under a tree when you see a thunderstorm approaching.

Featured image: Pixabay

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