Stephen Frost wrote: -- Start of PGP signed section. > * Bruce Momjian (pgman@candle.pha.pa.us) wrote: > > This patch disables page writes to WAL when fsync is off, because with > > no fsync guarantee, the page write recovery isn't useful. > > This doesn't seem quite right to me. What happens with PITR? And
PITR doesn't need page writes at all because it has a full backup the file system to start with. In fact with PITR the crashed file system isn't used at all (restored from backup). In fact there is a TODO to exclude full page writes from the PITR backup of WAL. > Postgres crashes? While many people seriously distrust running w/ fsync > off, I'm sure there's quite a few folks which do. > > > This also adds a full_page_writes GUC to turn off page writes to WAL. > > Some people might not want full_page_writes, but still might want fsync. > > Adding an option to not do page writes to WAL seems fine to me, but I > think WAL writes should be on by default, even in the fsync=off case. > If people want to turn it off, fine, for either case since we expect > they understand what it means to have it turned off, but I don't think > the two options should be coupled as is being proposed. That is a question I had in my mind. I added documentation that turning off fsync also disables full_page_writes, but we could decouple them and tell people to consider disableing full_pages_writes if they turn off fsync, basically suggesting they make the second change. Other opinions? -- Bruce Momjian | http://candle.pha.pa.us pgman@candle.pha.pa.us | (610) 359-1001 + If your life is a hard drive, | 13 Roberts Road + Christ can be your backup. | Newtown Square, Pennsylvania 19073 ---------------------------(end of broadcast)--------------------------- TIP 4: Don't 'kill -9' the postmaster
