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In a post on electronics.stackexchange.com (now deleted because off topic there) was explained, in details, the reason why is not advisable to disable an hard disk (pc not turned on, of course) simply detaching it from power supply unit. Please see below some quotes.

Now, by chance, I have changed upon racks for internal hard disk endowed with power switch "included for power saving or safe removal" like, as example, this one.

Therefore I wonder if what was elucidated before still holds here, or the tray is equipped with some device to resolve all the problems mentioned in that post.

As far as I can suppose at present moment, it seems unlikely that the switch breaks all four cables of the power supply unit.

I would not break the black cable, it leaves 7v across the 5v and 12v inputs, and with no ground, who knows what could happen. It may even send current through the data I/O and damage those. Even if there's no destruction mechanism in this state, I doubt it would come up cleanly when the connection was restored. Invest in a 2 pole switch, and break the red and yellow.

Next to @Neil_UK advise, do still use 2 black wires. Without knowing the reason for two wires do still question: why would the manufacturer use 2 black wires (and make more production costs) if 1 would be enough? (Manufacturer's reason could be current rating, splitting power ground and signal ground, etc).

Even if you switched all of the power lines you would still have the drive's I/O signals connected to a powered-up motherboard. There is a good reason why drives are controlled the way they are, with a combination of hardware and software.

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    The first link is broken (404) – gronostaj Mar 25 at 11:39
  • Sorry, the post has been deleted because "Questions on the use of electronic devices are off-topic as this site is intended specifically for questions on electronics design." Can I copy and paste its content here ? – glossa Mar 25 at 11:44
  • Assuming the hard disk has a SATA power connector, then you can hot swap it by design (see e.g. here, some pins are shorter). Trying that with an IDE power connector ("the four cables") may or may not work, very likely it won't, even if the data connecter is SATA. It's not clear what the "power switch" in your link actually does (maybe it slides the harddisk just a bit to remove the connector?), so no idea in this respect. Try to find out some details. – dirkt Mar 25 at 11:51
  • @glossa You can quote relevant parts and provide a link. Just add a note indicating that the original post is deleted and you're aware of it. – gronostaj Mar 25 at 11:53
  • Thanks for replyes! I have just now fixed my post. – glossa Mar 25 at 12:03

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