Thread: Fsync on/off For Various Filesystems/Platforms (Ending Note)
Damn... too quick with the "send" button. I forgot to mention : 1) the test involved usng copy to load the rows ! 2) The masured numbers were elapsed minutes:seconds for the load regards (again) Mark
Mark kirkwood <markir@slingshot.co.nz> writes: > I forgot to mention : > 1) the test involved usng copy to load the rows ! Still not much help. Was it a single COPY command, or a bunch of them? The fsync overhead is (and always has been) a per-transaction cost, so a benchmark that gives you no idea how many transactions were committed isn't much help. Also, if there was only one transaction commit in your 5-minute benchmark run, then I can see why fsync would be pretty irrelevant ... try something with one commit per inserted row if you want to see a bigger penalty ... regards, tom lane
Mark kirkwood wrote: > Damn... too quick with the "send" button. > > I forgot to mention : > > 1) the test involved usng copy to load the rows ! Oh, COPY. Remember fsync of WAL only happens at the end of a transaction, and with COPY, that is only once the table is completely loaded. No wonder you saw strange results. Also, someone reported ext3 as 50% slower than ext2, so again, your numbers are a surprise. -- Bruce Momjian | http://candle.pha.pa.us pgman@candle.pha.pa.us | (610) 853-3000 + If your life is a hard drive, | 830 Blythe Avenue + Christ can be your backup. | Drexel Hill, Pennsylvania 19026