Most energy efficient (home) setup

Jimmy Hess mysidia at gmail.com
Sun Apr 15 10:52:51 CDT 2012


On Sun, Apr 15, 2012 at 1:46 AM, Joe Greco <jgreco at ns.sol.net> wrote:
> Since we don't hear about Mac mini server users screaming about how
Do you hear of lots of Mac mini server users loading up 16GB of RAM?
----
> it's just a matter of time before your server's power supply fails, or

The difference is power supplies don't fail nearly as often as 1-bit
DRAM errors, except when subject to harsh conditions.    HDD errors
are comparably rare also;  and yet,  the drive surface of any HDD has
error correction codes,  because disk surfaces are subject to similar
problems.

Consumer desktop hard drives use non-ECC memory inside the drive for
the cache/buffer memory, to save $$$:    but it's typically only
12MB or so of memory,   so it's approximately  300 days  before you
have a 50% chance of a single bit error  caused by background
radiation, and those are good odds,
but nevertheless, people get corrupted files, so maybe they aren't that good.

Consider that the probability 16GB of SDRAM experiences at least one
single bit error at sea level,
in a given 6 hour period exceeds  66%  = 1 - (1 - 1.3e-12 * 6)^(16 *
2^30 * 8).    In any given 24 hour period, the probability of at least
one single bit error  exceeds 98%.    Assuming the memory is good and
functioning correctly;

It's expected to see on average approximately   3 to 4   1-bit errors
per day.  More are frequently seen.

Now if most of this 16GB of memory is unused, you will never notice
that over 30 days,  120 or so bits have been flipped  from their
proper value..


On the other hand,  if you have some filesystem read cache for a NAS
VM  or database
application in the effected space,  and  moderately important data is
being damaged
well,   that's just plain uncool



>
> ... JG
--
-JH



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