On 08/02/2016 02:33 PM, Bruce Momjian wrote: > My guess is that the bytes are there to detect problems where > a 512-byte disk sector is zeroed by a disk failure.
Does that seem plausible? (a) there is only one such header for every 16 512-byte disk sectors, so it only affords a 6% chance of detecting a zeroed sector, and (b) the header contains other non-zero values in fields other than xlp_pageaddr, so the use of a fixed value for _that field_ in zeroed tail blocks would not prevent (or even reduce the 6% probability of) detecting a sector zeroed by a defect. -Chap -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
