You said "local Reiser FS." Maybe repeat on one of the others, Ext3/JFS? Tom asked about hardware issues, is there nothing in syslog that relates to the timing of the event? I don't recall you responding in public to this. Maybe I missed it. Just musing... On Wed, Sep 13, 2006 at 12:50:26PM -0400, Tom Lane wrote: > "Mr. Dan" <bitsandbytes88@xxxxxxxxxxx> writes: > >> How are you doing the copies, exactly? SQL COPY command, psql \copy, > >> something else? > > > We've tried SQL COY and psql \copy and always get random results - 0,1, or 2 > > blocks of 25 rows missing. > > Hmph. If it happens with a SQL COPY command then psql seems to be off > the hook, and that also eliminates some theories about dropped TCP > packets and such. > > Would you check back in the source table for the COPY and see what the > ctid values are for the missing rows? I'm wondering about a pattern > like "the dropped rows of a group are all on the same disk page", ie, > what's being missed is one whole page at a time. > > If that's what's happening, the only very plausible theory I can think > of is that your disk drive is sometimes glitching and returning a page > of all-zeroes instead of what it should return. Postgres will not > complain about this in normal operation (because there are legitimate > error-recovery scenarios where a zero page can be in a table); it'll > just treat the page as empty. VACUUM will complain though, so the next > step would be to set up a test table by copying your large table and > then repeatedly run plain VACUUM on the test table. If you get sporadic > warnings "relation foo page N is uninitialized --- fixing" then we have > the smoking gun. Don't run this test directly on a valuable table, as > each such message would mean you just lost another page of data :-( > > FWIW, I spent several hours yesterday evening copying 6GB tables around > to see if I could reproduce any such problem, and I couldn't... > > regards, tom lane > > ---------------------------(end of broadcast)--------------------------- > TIP 3: Have you checked our extensive FAQ? > > http://www.postgresql.org/docs/faq --
