The manufacturers warrant these devices to behave on a motherboard with proper power hold up times, not in whatever enclosures.
If the enclosure vendor suggests that behavior on cable pull will fully mimick motherboard atx power loss then that is fraud. But they probably have fine print about that, I'd hope.
"The manufacturers warrant these devices to behave on a motherboard with proper power hold up times"
Thats an interesting point, doesn't 'power failure' also include potential failure of the power supply, in which case you might not get that time?
Or what if a new write command is issued withing the holdup time, does the motherboard /OS know about powerloss during those 16 milliseconds that the power is still holding?
'Power loss' or 'power failure' for a part designed to operate at ATX specs does not mean supply failure. Supply failure can cause anything up to and including destruction of all components and even death of operator.
Anyway, let's firm up how an SSD works and what the OS knows.
SSDs have volatile DRAM buffers as a staging area to use before writing to the flash.
Flush (OS ioctl) means the data is successfully residing in the volatile DRAM of the SSD.
This is all the OS knows and usually ever knows in the ioctl cycle.
If power is lost there is some time before the >16ms is up that power good signal is lost on the motherboard. The voltage on the 3.3V rail will probably also drop enough from nominal to let the SSD controller know it better gets its housekeeping in order. In other words, dump the DRAM somewhere permanent and deal with it on the next power up.
Anything the OS is doing in the interim will not likely be acknowledged as flushed so that's not a concern. The OS userspace write will never complete. That loop works fine.
The thing that gets people up in arms is that flush means the SSD has the data only in volatile memory and not necessarily in non-volatile storage.
All performant SSDs seem to work this way. They need buffers.
The larger form factor enterprise drives, which are maybe 25% more expensive, have PLP capacitor banks. These supply a solid 50ms of power. Some manufacturers supply oscilliscope screenshots and such.
Anything else seems to be variable in its approach to power loss, particularly the smaller, hotter M.2 parts .
Capacitor banks have issues like taking up space, causing inrush currents, gaining impedance over time, and mediocre reliability at the high temperatures that latest M.2 sticks experience.
> The larger form factor enterprise drives, which are maybe 25% more expensive, have PLP capacitor banks.
I wonder if there would be a market for a small board that contains the capacitors and passes the signals down to a M.2 female connector. The physical disconnect would probably help with the temperature as well (and the board could come with its own heatsink).
I want to revise my comments. There are indeed some capacitors on many M.2 boards -- not sure how much. It takes several mF or more to drive a few amps at 3.3V for some tens of milliseconds, which is not insignificant, so larger form factors are certainly at an advantage.
The tester is running the device out of spec.
The manufacturers warrant these devices to behave on a motherboard with proper power hold up times, not in whatever enclosures.
If the enclosure vendor suggests that behavior on cable pull will fully mimick motherboard atx power loss then that is fraud. But they probably have fine print about that, I'd hope.