Does an external hard disk, e.g. WD Elements, has to stand upright?

I would contact seagate directly and see what they say.

As long as you have good air flow it shouldn't matter too much. Hard drives can get hot.

It's Fine To Mount Hard Drives On Their Side Or Even Upside-Down - Stephen Foskett, Pack Rat

Doesn't matter, really. Just use common sense and don't lay things on it or otherwise block external air flow around it. Orientation is not important.

Mine is lay down but is sat on two thin pieces of foam to lift it off the bottom of the table. Average temp is about 40c.

I would contact seagate directly and see what they say.

And / or WD, yes. Do you have an e-mail address?

As long as you have good air flow it shouldn't matter too much.

Yes, but I would like to avoid even less than too much.

It's Fine To Mount Hard Drives On Their Side Or Even Upside-Down - Stephen Foskett, Pack Rat

Thank you for the link. "as long as it’s not tilted" means an oblique position? So does an angle of 5° harm? Or 10°? I do not think so, but may be an angle like 45° is meant.

Doesn't matter, really. Just use common sense and don't lay things on it or otherwise block external air flow around it. Orientation is not important.

Yes, I assume in server farms they will be mounted in many ways. But those drives won't be the cheapes hard disk like the above mentioned.
Generally I would lay down all drives although designed to stand upright (Elements, Expansion, MyBook, etc.) because it is saver.

Mine is lay down but is sat on two thin pieces of foam to lift it off the bottom of the table.

That (among other things) is another reason why I want to lay them lay down, standing upright on something like foam make their stand very instable. And beause of avoiding the noise.

Average temp is about 40c.

The SEAGATE Backup Plus HUB and MyBook have a temperature of about 48° without stress and when copying, synchronizing up to 58°. I hope, they are designed to withstand such temperatures. My external 5 TB WD Elements runs at about 10° less.

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As long as they are not moved during use

What exactly does that mean. Not to move the drive at all while it is running? To minimize the risk? If one carefully moves the drive nothing will happen, I would think. Or does it cause stress for the drive if it is moved when it is running?

Spoilo said:

What exactly does that mean. Not to move the drive at all while it is running? To minimize the risk? If one carefully moves the drive nothing will happen, I would think. Or does it cause stress for the drive if it is moved when it is running?

I would imagine that's referring to the heads possibly getting jostled. At 7200rpm, it's like picking up a spinning Gyro.

My WD drives, 2 USB and 2 NAS, have ventilation slots on one end so I set them up on the other end to allow warm air upward and out. Their logos are oriented the same way.

Berton said:

My WD drives, 2 USB and 2 NAS, have ventilation slots on one end so I set them up on the other end to allow warm air upward and out. Their logos are oriented the same way.

That's handy. Dirt dumb USB externals don't have those niceties.