ZimaOS 1.6.0 fixed one real disk-standby bug, but this source proves that fix did not solve every USB enclosure. IceWhale's official 1.6.0 release notes say smartd had been intermittently waking disks and preventing normal sleep. After updating to the final 1.6.0, users with TerraMaster D5-300C and D4-320 enclosures still reported that their USB HDDs would not spin down.
The correct conclusion is narrower: 1.6.0 fixed one system-side wake source; USB bridge/enclosure behavior remained setup-dependent.
Disk Standby Is a Real ZimaOS Feature
ZimaOS introduced a Disk Standby option in earlier releases. The source users were not asking whether standby existed at all; they were reporting that USB-attached disks ignored or failed to sustain it.
ZimaOS 1.6.0 Officially Fixed smartd Waking Sleeping Disks
The official 1.6.0 release notes explicitly list a fix for disks being unable to enter normal sleep because smartd woke them intermittently.
See the official 1.6.0 disk-standby fix.
The Original Poster Still Failed After Updating to Final 1.6.0
alexstamos upgraded from beta to final 1.6.0 and reported that the problem remained. Their TerraMaster D5-300C contained three RAID 5 members plus one standalone disk, and none entered sleep.
Another TerraMaster D4-320 User Reproduced the Same Problem
jumpingflash said the D4-320 spun down correctly on other computers but not under ZimaOS 1.6.0. A later D4-320 owner made the same comparison with other Linux distributions.
Other USB HDDs Did Spin Down Normally
isanto1306 reported three WD USB hard drives sleeping successfully. That is equally important evidence because it prevents the opposite overstatement that ZimaOS cannot spin down USB drives.
hd-idle Was a Community Workaround
The original poster said they managed to get drives sleeping after about ten minutes by experimenting with hd-idle. They did not publish a complete reproducible ZimaOS installation procedure.
Another User Forced Standby with smartctl and a systemd Timer
ssimon posted a script that periodically ran smartctl -s standby,now against the USB disks and scheduled it through systemd.
This is community code, not IceWhale's official standby implementation. Forcing standby every few minutes can also fight active workloads if the script does not check for I/O first.
Do Not Force a Busy Disk to Sleep
- Confirm no backup or migration is running.
- Confirm no RAID rebuild/scrub is active.
- Check Docker apps and indexing jobs.
- Verify the enclosure supports the standby command.
Do Not Claim a D4-320-Specific Fix Without Current Evidence
Current ZimaOS is newer than 1.6.0, but the public 1.7.1 notes do not provide a specific TerraMaster D4-320/D5-300C spin-down fix. Re-test the current stable release and exact enclosure firmware before applying an old timer.
USB-SATA Bridge Firmware Can Change Standby Behavior
A multi-bay USB enclosure is not electrically or logically identical to a directly attached SATA disk. The USB bridge may translate, ignore, or reinterpret ATA standby commands, and some enclosures poll disks internally.
That explains why the same HDD can sleep correctly when connected another way but stay active behind a particular DAS bridge.
Differentiate “Never Sleeps” from “Sleeps Then Wakes”
A disk that never enters standby points toward unsupported commands, constant I/O, or enclosure behavior. A disk that sleeps and wakes every 30–60 minutes points toward periodic polling or services such as SMART/storage checks.
The 1.6.0 smartd fix addresses the second pattern, not every possible first pattern.
Measure Standby State Without Waking the Disk
Some status queries themselves can wake a sleeping disk or be reported incorrectly through a USB bridge. Use enclosure-compatible, non-waking checks when possible and compare physical behavior—spin noise, power draw, temperature—with the reported software state.
Do Not Turn Spin-Down Frequency into a Universal Drive-Life Formula
Source users were understandably worried about power and wear, but statements such as “the HDDs will not last a year” were not supported by drive-health evidence in the thread. Frequent start/stop cycles and 24/7 rotation have different tradeoffs depending on drive design and workload.
Choose a standby interval that matches your usage rather than forcing very short cycles simply to minimize spin time.
USB HDD Spin-Down FAQ
Did ZimaOS 1.6.0 fix a disk standby bug?
Yes. IceWhale fixed smartd intermittently waking sleeping disks.
Did that fix every TerraMaster USB enclosure?
No. Multiple source users still reported no spin-down on D5-300C and D4-320 hardware after final 1.6.0.
Were hd-idle and smartctl timers official fixes?
No. They were community workarounds and should be tested carefully on the exact enclosure.
