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Added some of Fatdog's code to EasyOS
due to a issue with a external usb3 mechanical HDD based boot where the heads are just being dropped at shutdown. Thought that the Fatdog code would cure the issue, but seemingly that isn't the case. The device does indeed stop, but near immediately starts back up again, such that by the time the power is actually cut the HDD heads still end up just being dropped. Posting this cross post as I'm unsure as to whether it could be a similar matter for Fatdog.
There is some discussion at this link by someone with similar concerns.
https://bbs.archlinux.org/viewtopic.php?id=261479
Μακάριοι οι καθαροί στην καρδιά * επειδή, θα δουν τον Θεό.
dogcat wrote: Thu Jun 09, 2022 10:58 amThere is some discussion at this link by someone with similar concerns.
https://bbs.archlinux.org/viewtopic.php?id=261479
Quoting from a link off that link:
Generally modern HDDs have a mechanism that automatically parks the heads on power loss, fully removing them from the spinning platter. You hear a click from the inside when that happens.
That has always been my understanding also.
In my particular case the heads are parking and the device halting (light goes out), but near immediately restarting again, with the read/write (in my case white) led flashing ... just as the power is cut and the heads 'scraping platter' sound is heard rather than the 'dink' of the heads having been correctly parked. Worst I suspect than if the light were just blue (usb hdd on/available but idle).
I found a interim solution of cutting system power pretty much immediately after the usb hdd STOP trigger, but that's not a very clean solution.
Fundamentally it looks like /aufs umount fails, leaving it still mounted and the drive active, primarily because the main sfs hadn't been copied to ram (drive left 'forced mounted' boot style).
The major issue is that seemingly some usb hdd's can rebound back into life again near instantly after having been 'stopped'. USB : oh I've been stopped ... OK. I'm still attached and now /aufs is looking for me so I jump back into high activity life again to service that ... and just then the power gets cut and the heads all crash against the platter.
(PS I should have mentioned that the USB HDD gets its power via the usb port, isn't separately powered. I suspect if it were then things would be cleaner).
