7 popular errors when connecting equipment

I wouldn’t want to upset anyone, but even the most “smart” data center - with redundancy according to the N circuit in the cube and generally your own - is not yet a guarantee of the smooth operation of the equipment: this equipment itself, first of all, needs to be connected correctly.

“Thank you, Cap!” - my reader will condescendingly smile, and I will answer him: no thanks, go better to the data center and check your racks again. Yes, yes, the same ones with whom a hundred years as everything is in order. You won’t believe how often regrettably happens with just such “problem-free” racks. I even sketched a checklist.
So, what you should NOT meet on this afternoon walk:

1. A server, storage or network equipment about two power supplies connected for some reason to one PDU *
That seems to be the alphabet - but you still check. It happens.

A variation on the same topic is an ATS, plugged into the same PDU with both power cables .

To avoid: ATS (automatic transfer of reserves) - this is such a contraption by which equipment with one power supply is connected to two PDUs (and, therefore, to two beams) - for example, network: switches, routers, that's all.

Suppose, by someone's distraction, the ATS, to which this is all connected, is powered from one PDU. What is this fraught with? If the corresponding beam disappears, the equipment with such an automatic transfer switch will, of course, turn off - and if it is network hardware, you will completely lose contact with the entire rack. It doesn’t sound very good, agree.

2.Equipment with one power supply connected at all without automatic transfer switch .
Bad, bad idea. I understand that a penny saves a ruble - but it’s important for you that it also works smoothly, right?

3. Load ABP more than 75-80%.
What is the ambush: when starting and rebooting, the equipment consumes much more current than in normal operating mode. Accordingly, if there is no “reserve” of ABP for such one-time “bursts”, when you start / restart, you simply “knock out traffic jams” and hello.

4. Equipment connected to adjacent racks
Perhaps, it would seem witty to “ship” a bit of power consumption to the neighboring “cabinet”, since it is idle unused, while there is nowhere to hang next to what is called. And now the backfill question: what do we have connected to which beam in the end? A? Nobody in the know? That's it.

There is still such a nuance as the heat generated by the equipment, and the risks of local overheating of the rack, loaded with this equipment “to the eyeballs”. Overheating and mess with the wiring - not the best help in the IT economy, believe me.

5. Overloaded PDU sections
I'll start from afar: the PDU has sections, and it's not just that. Each section of the standard PDU, the total power of which is, say, 32A, is designed for a current of not more than 16A. But it’s not designed for 20A. And at 25 either. Even if the second section is completely free. Such a nuance.
Now imagine that someone (with the brightest, we will notice in brackets, intentions) neatly fills the rack with equipment and ABP - for example, from the bottom up - and, of course, connects the whole thing also strictly from the bottom up. To just without a mess and beautiful.

It would seem that he did everything right, and 32A has not been scooped up yet, but only 20 - live and rejoice. Then, one fine morning in the data center, one power beam is turned off - and suddenly (!) On the “overheated” section, the circuit breakers are activated and this whole section (with the equipment connected to it, yes) is safely turned off. Elegant, right? Do you want yourself this?

6. A rack overloaded with equipment so much that it is forced to “feed” in normal mode from two beams at once, one of which is actually a backup.
Here it is: the reserve, which is involved in a regular situation - it’s as if not a reserve, or something ... The
good news is that there are human ways to increase the power of the rack - and without disconnecting the active equipment. Intrigued? Then write down:

• firstly, you can add a couple more PDUs of the same power and all new equipment ... well, then on your own, not small;
• secondly (the option is more exotic), you can replace the current PDUs with more powerful ones

Here, perhaps, some skill will be required, but in general everything, again, is transparent: put more powerful machines, lay a more powerful cable, install a new (concurrently more powerful) PDU next to the old one - and calmly switch equipment from one PDU to other. Well, that’s how calm it is: if you suddenly have one oversight on our checklist item, it can be awkward. And if everything is clear, it will pass without interference. Next, repeat the procedure with the second PDU - and vivat! You can go for a smoke.

7. You just do not laugh, but ... check the indication. No, really, check it out .
It happened to myself: they connected the ABP, everything seems to be ok, but a bad contact, or an inoperative wire, or a cable is not fully inserted ... continue?

The same thing with two power supplies: everything looks fine - the equipment works, there are no problems. But in fact, one of the blocks died long ago without leaving a will.

In general, do not be lazy once in a while it will turn out to check the equipment that is especially dear to your heart for the presence of red light bulbs or the absence of green ones in the right places. You yourself will say thank you later.

On this, our modest hit parade of absurdities when connecting equipment has been exhausted. Finally, a picture about how to do it. Your continuous service and uninterrupted benefits.

* Power Distribution Unit - a block of outlets, if in a simple way