Curt Sampson wrote: > On Thu, 25 Apr 2002, mlw wrote: > > > ...but my gut tells me that using 16K blocks will increase performance > > over 8K. Aleady I have seen a sequential scan of a large table go from 20 > > seconds using 8K to 17.3 seconds using 16K. > > You should be able to get the same performance increase with 8K > blocks by reading two blocks at a time while doing sequential scans. > That's why I've been promoting this idea of changing postgres to > do its own read-ahead. > > Of course, Bruce might be right that the OS read-ahead may take > care of this anyway, but then why would switching to 16K blocks > improve sequential scans? Possibly because I'm missing something here.
I am almost sure that increasing the block size or doing read-ahead in the db will only improve performance if someone is performing seeks in the file at the same time, and hence OS readahead is being turned off. -- Bruce Momjian | http://candle.pha.pa.us [EMAIL PROTECTED] | (610) 853-3000 + If your life is a hard drive, | 830 Blythe Avenue + Christ can be your backup. | Drexel Hill, Pennsylvania 19026 ---------------------------(end of broadcast)--------------------------- TIP 2: you can get off all lists at once with the unregister command (send "unregister YourEmailAddressHere" to [EMAIL PROTECTED])
