On Oct 8, 2009, at 10:28 AM, Dan wrote:
> What got me to thinking is this article on ars... > > <http://arstechnica.com/business/news/2009/10/dram-study-turns-assumptions-about-errors-upside-down.ars > > > With the caveat that this is memory studied under high utilization regime; this is RAM in datacenter systems. The study showed that failure rate was proportional to utilization, and "About 8 percent of DIMMs were responsible for over 90 percent of the errors". If only 8% of the systems display the error, is it worth the added costs of adding ECC RAM to the 90% of systems that don't have these failures? This is amplified by the findings that hard errors predominate. (which is the same thing as that 8% figure...these are faulty DIMMS, not cosmic rays) Finally, the error rates only appear high because previously published error rates are so staggeringly (and artificially) low. In the entire study (and remember, these are 24/7/.999nnn uptime systems running at a high utilization all the time, hardly comparable to virtually any systems owned by people on this list) less than a third of the systems suffered *any* memory failures in a year. SO to recap: Under datacenter utilization regimes in server systems (much more rigorous than the average computer user), 90% of all memory failures are caused by 8% of the DIMMS, and 66% of the systems saw no failures in an average year. picking RAM out of a hat, Data Memory Systems sells 1G DDR2 PC2-5300 667MHz DIMMS for the following prices: Type Price %premium Non-ECC $23 -- Unreg ECC $36 56% Reg. ECC $39 70% The cost/benefit ratio just isn't there...the conclusions to be drawn from this article are that DIMM manufacturers need better testing and QC protocols to identify that 8%; charging 10% more per DIMM for adequate testing is much more likely to bring about real, widespread improvements than spending 60 or 70% more per DIMM for error correction. Finally there's the issue of what the errors actually mean. What happens if one bit flips in a memory representation of a jpeg? -- Bruce Johnson University of Arizona College of Pharmacy Information Technology Group Institutions do not have opinions, merely customs --~--~---------~--~----~------------~-------~--~----~ You received this message because you are a member of G-Group, a group for those using G3, G4, and G5 desktop Macs - with a particular focus on Power Macs. The list FAQ is at http://lowendmac.com/lists/g-list.shtml and our netiquette guide is at http://www.lowendmac.com/lists/netiquette.shtml To post to this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/g3-5-list -~----------~----~----~----~------~----~------~--~---
