On Jan 30, 2010, at 8:58 AM, matthew patton wrote: > please forgive the 'stupid' question.
This is not a stupid question, it is actually a good question that is frequently asked. > Aside from having a convenient hash table of checksums to consult and upon > detection of a collision knowing we are dealing with a duplicate, why > checksum data when the memory bus, PCI-e/x bus, sata/sas bus, and the hard > disk itself use Reed-Solomon (or similar) encoding to store/transmit ECC > along with the data? > > Where is this "silent data corruption" supposed to occur? And is the > probability of preventing/catching an occurance a realistically relevant > value? I find that when people take this argument, they assuming that each component has perfect implementation and 100% fault coverage. The real world isn't so lucky. The seminal paper for advocating end-to-end data protection is: "End-to-End Arguments in Systems Design," by Saltzer, Reed, and Clark, MIT. http://web.mit.edu/Saltzer/www/publications/endtoend/endtoend.pdf Like the best seminal papers, it is clear and concise. -- richard _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
