If on searches the OS3 My Cloud subforum for “sleep” they’ll find numerous past discussions about sleep mode issues with the OS3 My Cloud. Many have found their OS3 My Cloud quite often does not enter or does not stay in Sleep Mode. That their unit is cycling in and out of Sleep Mode or simply doesn’t enter sleep mode at all. Many have had success (sometimes limited) disabling certain services on the OS3 My Cloud using SSH. Much past discussion on which services to disable can be found using the forum search feature.
There is much thought and opinions if repeated starting and stopping a hard drive is worse than leaving the drive running 24/7. Generally the OS3 My Cloud units used WD Red drives and those drives are designed for 24/7 operation. WD claims for example WD Red drives have a (mean time between failures) “MTBF of up to 1 million hours.” One million hours equals approximately 114 years. In reality hard drives can and do fail for any reason. They can last years before failing, or can fail in hours or days after first boot.
It is generally a very good idea to have a backup of any data one stores on the My Cloud. The My Cloud includes a backup feature called Safepoint (v4.x firmware) or Backup (v2.x firmware).
