On Sun, Apr 15, 2012 at 1:46 AM, Joe Greco <jgreco@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