>>>>> "cg" == Christopher George <cgeo...@ddrdrive.com> writes:
cg> Nothing, the DDRdrive X1's data integrity is guaranteed by the
cg> attached UPS.
I've found UPS power is less reliable than unprotected line power
where I live, especially when using bargain UPS's like the ones you
suggest. I've tracked it for five years, and that's simply the case.
When devices have dual power inputs I do plug one into the UPS though.
I've also found unplanned powerdowns usually occur during maintenance
because of people tripping over cords (networking equipment likes to
put A/B power on opposite sides of the chassis. Thanks for that, to
those who do it.), dropping things, bumping power strip switches
(which should not exist in the first place), provoking crappy devices
(ex poweron surges causing overcurrent), mucking around with the
batteries, or confusing highly-stupid UPS microcontrollers over their
buggy web interfaces (``reset controller''), clumsy buttonpads (a
single on/off/test button? are you *CRAZY*? and sometimes I have to
_hold the button down_? What next, double-pressing? there's on,
there's off, but what about the ``off-but-charging'' state: how's it
requested and how's it confirmed? hazily? thanks, assholes.). Your
decision to use UPS power is based on the imaginary scenario you walk
us through: building loses line power for X minutes, UPS runs out.
Obviously I'm familiar with the scenario but honestly I've not run
into that one in practice as often as other ones, which is why I call
it fantasy.
cg> NAND only provides an optional (user configured)
cg> backup/restore feature.
so, it does not even attempt to query the UPS? How can it live up to
the ideally-functioning-UPS protection scheme you describe, then? To
do so it needs UPS communication: it'd need to NAND-backup before the
battery ran out, so it needs to get advance warning of a low battery
from the UPS. It'd also need a way to halt the computer, or at least
to take itself offline and propogate the error up the driver stack, if
the UPS has not enough charge to complete a NAND backup or of the UPS
considers its batteries defective.
Personally, I don't care if the card talks to the UPS, because I think
realistically if you take the cases when power stops coming out of a
UPS and overlap them with the cases when the UPS provided warning
before the power stopped coming out, there's not much overlap.
Spurious warnings and sudden shutdowns are *more* common over the life
of the units I've had than this imaginary graceful powerdown scenario.
Finally, data that's stored ``durably'' needs to survive yanked
cables. IMHO most people who are certain cables will never be yanked
or are willing to take the risk, would be better off just disabling
the ZIL rather than using a slog. Then you don't have to worry about
pools failing to import from missing slog if you do yank a cable,
which is a better tradeoff.
NAND storage therefore needs to be self-contained, like a disk drive,
to be useful as a slog. The ANS-9010 comes closer to that than this
card, though I don't know if it actually delivers, either.
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