7 popular errors when connecting equipment

I would not want to upset anyone, but even the most “elegant” data center - with redundancy under the N scheme in a cube and your own in general - is not a guarantee of the equipment’s uninterrupted operation: this equipment itself must first be properly connected.

“Thank you, Cap!” My reader will condescendingly smile, and I will answer him: it’s not worth thanks, go better to the data center and check your racks again. Yes, yes, those with whom a hundred years everything is in order. You will not believe how often it is with such “problem-free” racks that the most regrettable happens. I even sketched the checklist.
So, what should NOT you meet on this afternoon walk:
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1. Server, storage or network equipment on two power supply units connected for some reason to one PDU *
That seems to be the alphabet - and you still check. It happens.

A variation on the same topic - AVR, with both power cables stuck in the same PDU .

In order to avoid: AVR (automatic input of a reserve) is such a thing by means of 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, due to the distraction of someone else, the ATS, to which all this is connected, is powered by a single PDU. What is it fraught with? If the corresponding beam disappears, the equipment with such AVR will of course turn off - and if it is network hardware, you will lose connection with the entire rack. It does not sound very, agree.

2. Equipment with one power supply unit, connected without any automatic transfer switch .
Bad bad idea. I understand that the penny is saving the ruble, but it’s important for you that it also works smoothly, right?

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

4. Equipment connected to adjacent racks
Perhaps, someone will seem witty to “ship” a little power to the neighboring “cabinet”, since he stands idle under-utilized, as long as he has no place to hang him near. And now the question of backfilling: what is there to which beam is connected in the end? BUT? No one in the know? This is it.

There is also 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 laying of wires - not the best help in the IT industry, believe me.

5. Overloaded PDU sections
I'll start from afar: the PDU has sections, and this is all for a reason. Each section of a standard PDU, the total power of which is, say, 32A, is designed for a current of not more than 16A. And on the 20A is not calculated. And at 25 either. Even if the second section is completely free. Such is the nuance.
And now let's imagine that someone (with the lightest, we will notice in brackets, intentions) carefully fills the rack with equipment and the ATS - 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 yet been exhausted, but only 20 in all - live and rejoice. Then one fine morning in the data center one power beam is disconnected - and suddenly (!) On the “overheated” section the automatic circuit breakers are triggered and the whole section (with the equipment connected to it, yes and yes) is safely disconnected. Elegant, right? Do you want this?

6. A rack overloaded with equipment so much that it has to “feed” at once from two rays at once, one of which is actually a backup one.
There is such a thing: the reserve, which is involved in a regular situation, - it is, as it were, no longer a reserve, or something ...
The good news is that there are human ways to increase the power of the rack - and without turning off the active equipment. Intrigued? Then write down:

• first, you can add a couple more PDUs of similar capacity and all the new equipment ... well, then, not small ones;
• secondly (the more exotic option), you can replace the current PDU with more powerful ones

Here, perhaps, some skill will be required, but on the whole everything is, again, transparent: put more powerful machines, run a more powerful cable, install a new (in combination more powerful) PDU next to the old one - and quietly switch equipment from one PDU to other. Well, that is, how calm: if all of a sudden you have oversight on item one of our checklist, it can be embarrassing. And if everything is clear - will pass without interference. Then repeat the procedure with the second PDU - and vivat! You can go for a smoke.

7. You just do not laugh, but ... check the display. No, really, check it out .
It happened at the very beginning: they connected the AVR, everything seemed to be ok, but what about a bad contact, or a non-working wire, or is the cable completely loose ... continue?

The same goes for two power supplies: everything looks fine - the equipment works, there are no problems. And in fact, one of the blocks died long ago, leaving no testament.

In general, do not be lazy as soon as you manage to check the equipment that is especially expensive for your heart for the presence of red light bulbs or the absence of green lights in the right places. Then thank you yourself.

On this our modest hit parade of absurdities when connecting equipment is exhausted. Finally, the picture is about how to do it. Continuous service and uninterrupted goods.

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