Spin up/downs puts wear on the motor and its bearings. Ok, there is no 100% clear answer, it always “it depends”-type of situation 
When you research on the internet, you’ll find many reasons (for various POVs). I think I’ll 24/7 my main unit, the backup unit though I may consider with the “sleep standby”-approach (or fully turning it off either), as that one likely is maybe 1x/d or 2x/d active. And the 2nd backup unit may even run only on a weekly schedule, so turning it off for most of the time seems reasonable.
I guess running the drives 24/7 doesn’t put any wear on the motors and their bearings, only spin ups/downs do 
. I’ll go with my knowledge from having worked in the HDD field.
Okay back on topic, thanks @777-Spider for furthering this fix.
Well, it was not an xor-argument obviously Any kind of operation will bring wear, just frequent turn on/offs (emphasis: frequent) are really not great for HDDs.
For any interested in fact over opinion regarding drive standby:
Typical rated (ymmv depending on your actual drive specs) spindle spin up/down cycle rating of a non-24/7 drive is 50,000. 50,000 cycles / 10 spin ups/downs per day (about double that of my own use case) = 5,000 days. That’s ~14 years, more or less depending on your use case.
Non-issue as modern drives are designed for it. My NEWEST NAS drives are 12 years old now. I just ran the entire array through all SMART tests (including comprehensive cycle), as well as multiple 0/1 write/verify/read/verify cycles. All good, drives are now in my new Zima OS NAS build. With 3-2-1 backups of course.
Just food for thought imagine all the pollution saved not running millions of household use case drives/pc’s/nas’s 24/7…
Because of described problem, wake up every 30 minutes: 50 000 / 24 [per day] = 2083 days ~5,5 year.
In my scenario, access to data on HDD few times per week (like 5), 50000 / 5 [per week] = 10000 weeks ~192 years 
Energy savings: when 2 disk are sleeping ~ -18W (measured). Usage time weekly ~18h max, 150h - sleeping. (Total consumption 22W HDD sleeping vs 40W spinning)
That around ~140 kWh yearly savings. You can say it not much, but it is 40% energy saving for my server!
Not bad for single working setting.
My use scenario, already described. NAS 24/7, has containers and 2x SSD drives (RAID 1), but large data are on 2 x HDDs (RAID1)
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Looks like I will have to move on from my ZimaOS evaluation. The standby issue is a showstopper for me, compounded by the immutable nature of the product which prevents users from addressing it before devs are available to do so.
Will revisit to see if things evolve.
Thanks for your feedback. We’ve fixed it in the next version. If you’d like to experience it earlier, I can invite you to join the beta testing group. Would you like to join?Thanks for your feedback.
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