Is internal or external HDD more reliable for backup

[Rainmain]

For regular weekly backups of large 5tb+ data, is it better to use an internal HDD that is online 24/7, or a external USB drive that only is on when backing up?

The reason I ask is I noticed many old IDE drives that sat unused in boxes in cool dry storage for years failed.
The same drives that were online for 24/7/365 just keep ticking it seems for decades.
I recently learned that drives should spin regularly to keep in top shape.
Would once a week be enough to keep the HDD in top shape?

[labtech]

have both

[jermy]

Having only a backup drive connected 24/7 you risking the backup drives data in case you get infected with a virus like lucky for example

[day1data]

Don't keep the backup drive connected 24/7 as previously said.
We are getting a lot of drives come in with Ransomware lately and the backup is also compromised because the backup drives were left plugged in.

Regardless of brand or size of drive they all just about have the same chance of failure. Aside from Seagate DM series drives because they have high failure rate.

But i would say run the backup once a week and then set the drive auto disconnect when the backup is complete.

[Rainmain]

Thanks. It's to bad Windows can't power down/suspend internal drives. Even if a drive spins down, MS wakes it randomly. I guess a keyed SATA bay would work.

I've noticed the external's tend to get screwed up by moving or lousy ventilation and power.

[jermy]

I've noticed the external's tend to get screwed up by moving or lousy .

then use a rg45 (network) connection to store it in appropriate place and condition (ventilation and power...) far away beyond reachable.
you have 100M/330FT length to find the appropriate place and condition to deal with, problem solved

[NRA]

They say the more precise and tinier moving parts (mechanics), the less reliable it is.
So, if it's not about flash/stream backups, I would go for a 'fatter' 5" type, because some tinier 3" counterparts are rather hot due to their form-factor.

It appears there are so many factors (vendor/factory/serial/number of platters/arrangement/usage and so on) to consider, that's why for spacious needs I prefer clouding (servers-based backup).