If the new SAS/SATA HDD does not spin up in the server: disable the Power Disable Feature

Do you install new SAS-12 or SATA-600 hard drives into a self-assembled server or workstation, and they do not start and are not detected? The controller does not see the HDD, there is no sound of the spinning platters and the cracking of the heads? Even if the disk has worked in another server before, it does not start either in the disk cage or when cables are connected directly? Most likely, you bought the disk at seconadry market or from an unofficial seller, but do not rush to apply to the warranty or return the money, as the solution may be simple or cheap: it is possible that your HDD supports the Power Disable Feature technology, which prevents it from starting in the server. This is a fairly old problem, but there is not much information about it on the web, and the solution is simple and trivial.

TL:DR The easiest way is to connect the power supply via a Molex-SATA adapter

Both SAS and SATA drives are connected to the power supply via SATA connectors (SAS via SAS-Fan-out cables, and SATA directly), most often even passive disk cages have such a connection, and if this is the case in your server, then try connecting one hard disk or the entire basket not directly to SATA-to the power supply connector, and through the Molex-SATA adapter.

Переходник Molex-SATA

This simple trick disables the Power Disable Feature, and the disk starts. You keep the warranty on the HDD, on the power supply and on the disk cage, and the solution to your problem costs about $ 3 and five minutes of time spent.

If there is no adapter at hand, and you need a solution right now?

The second option is to take the SATA power cable going to the disks or basket and cut the extreme wiring, which is right next to the corner of the SATA connector. Usually, such power cables have 5 wires (they can be installed in pairs), and if the insulation on them is colored, then the wiring you need is orange, and if the cables are monochrome, then it is simply first. near SATA-angle. According to the specification, this wiring has the designation 3.3V, and in expensive power supplies it can be pulled out of the SATA connector by disassembling the latter, but it is easier to take side cutters and bite it off from all connectors.

Отрезаем провод

This option, of course, will void your warranty on the power supply, but anyway, this is the solution.

If the disk cage is connected by some non-standard cable, and no one will let you get there?

You need to take the hard drive in your hands and seal/varnish the three right contacts on the side of the SATA corner or SAS ledge. For such a procedure, you can use a thin strong adhesive tape or nail polish. In which case, traces of such a procedure can be easily removed (including wiping off the varnish) and the disk will retain its warranty appearance.

There is an opinion that it is possible to cover up only the third contact on the right, because it is he who is responsible for Power Disable.

I believe that it is physically easier to close three contacts than one.

And what kind of bullshit is this (if not to say coarser)?

The fact is that the SATA/SAS power supply standard included an additional +3.3 V power bus, which has never been used anywhere or by anyone. These are the so-called "reserved options for the future". Conventional hard drives require two supply voltages: +5V and +12V, which are supplied together with two grounding wires to eliminate voltage distortion on the common ground when starting several drives at once. The four wires that come to the Molex power connector are quite enough for the hard drive to work for years without questions, but there is also a 5th wire through which a voltage of +3.3 V. On old hard drives, there are even +3.3V pins on the HDD board were not connected, that is, the voltage from the power supply unit came to the disk, but "hung in the air". Bright minds were not satisfied with this situation, and the Power Disable Feature technology was invented.

Its essence is that if the hard disk sees a voltage of +3.3 V on the input pin, it turns off if it was turned on or does not turn on if it was turned off. This is done so that you can remotely, programmatically turn off/turn on the hard drive without touching it with your hands. If the HDD freezes, this procedure helps to return it to work automatically, which is important when, for example, the disk stumbles upon some kind of surface error.

That is, technically, it is assumed that the hard disk is installed in a cage on which the voltage is +3.3B comes via the SATA connector, but it is not fed to the HDD until the right moment, and the disk works as if nothing had happened. If the data center operator needs to make a Power Cycle for the HDD, he sends a command through the server management system, and the backplane briefly supplies +3.3B on the HDD, it turns off/on and works on.

Is it okay that the +3.3 V voltage is supplied to the SATA connector on power supplies all the time?

But this is not a question for me, but for "bright minds". The power supply, by itself, is a pretty stupid device and rarely controlled. Naturally, it always gives out the necessary +3.3 V, well, at least in order of the "smart disk cage" itself choosing which disk to send to reboot if necessary. Therefore, the hard drive, seeing +3.3V at the input, just goes into a cyclic Power Off state and does not start at all. And this applies even to very good, high-quality new power supplies from 2021-2022, which will work in 24x7 mode for 5 and 10 years and can honestly be used in servers and workstations. That is, all responsibility for using Power Disable falls on the active disk cage, and the power supply has nothing to do with it.

Another question: why not do the opposite - in the presence of +3.3V at the input so that the disk works, and in the absence - powers off? Well, here, apparently, it's already a matter of compatibility with disk baskets, which do not know how to Power Disable, and for which + 3.3V does not come from the power supply.

Are all hard drives affected by this problem?

No, it is important to understand here that if you are faced with this problem, it is only because you should not have this hard drive in principle. The Power Disable function is optional, it is included in hard drives for storage manufacturers and branded servers where active response boards are installed in the cages, and figuratively speaking, companies such as Dell, HPE, EMC or HGST specifically order disks with this function to facilitate the process of managing storage for their customers. Such hard drives are not available for retail sale: from birth they work in branded storage systems, and then they are physically destroyed (see the article on methods of disposal of hard drives in data centers). So if you got such a disk in your hands, most likely it's the sysadmin selling a replacement fund or a decommissioned storage, well, or it's the seller's mistake, if the disks were bought do not understand where and it's not clear from whom.

Nevertheless, for some hard drives, manufacturers indicate the presence or absence of the Power Disable function, for example, there is such a document at WDC, but this is a pleasant exception, but in general, look for yourself. It is known for sure that server SAS-600 HDDs do not have this problem, but with the SAS-12, the whistle begins. I have a Seagate Exos 7E8 ST4000NM003A on my desk, which does not work without modification of the SATA power supply, and there is not a word about it in the datasheet. The situation is exactly the same with the Toshiba AL14SEB12EQ - there is not a word in the datasheet that the disk supports the Power Disable Feature. But the Toshiba MG08SDA400E does not have this problem, and works on conventional, unmodified cables.

Therefore, when assembling a modern server with hard drives (SAS and SATA), it is better to bypass the Power Disable Feature at the level of power cables in advance, so as not to tear your hair in the future when the newly purchased HDD simply refuses to start.


Buying a hard drive for storage, you may encounter several problems. For example, the drive may not be formatted in 512 Bytes, and you will have to format it at a low level. Or HGST hard drives can be tightly locked for use only in the vendor's storage, and such drives cannot be flashed. The Power Disable Feature function is the most harmless of them, if you do not know about its existence, then it will rattle your nerves significantly, but if you know, it will take a few minutes to solve the issue.

Michael Degtjarev (aka LIKE OFF)

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