On Thu, 17 Feb 2005 17:54:38 +0300 (MSK) "E.Rodichev" <[EMAIL PROTECTED]> wrote: > On Thu, 17 Feb 2005, Christopher Kings-Lynne wrote: > > >> The general question is - does PostgreSQL really need fsync? I > >suppose it> is a question for design, not platform-specific one. It > >sounds like only> one scenario, when fsync is useful, is to > >interprocess communication via> open file. But PostgreSQL utilize IPC > >for this, so does fsync is really> required? > > > > NO! > > > > Fsync is so that when your computer loses power without warning, you > > will have no data loss. > > > > If you turn it off, you run the risk of losing data if you lose > > power. > > > > Chris > > This problem is addressed by file system (fsck, journalling etc.). > Is it reasonable to handle it directly within application?
NO again! Fsck only fixes up file system pointers after a crash. If the data did not make it to the disk, no amount of fscking will put it there. I'm not positive but I think that journalled file systems also need fsync to guarantee that the information gets journalled but in any case, journalling only helps if you have a journalled file system. Not everyone does. This is not to say that fsync is always required, just that it solves a different problem than all those other tools. -- D'Arcy J.M. Cain <darcy@druid.net> | Democracy is three wolves http://www.druid.net/darcy/ | and a sheep voting on +1 416 425 1212 (DoD#0082) (eNTP) | what's for dinner. ---------------------------(end of broadcast)--------------------------- TIP 2: you can get off all lists at once with the unregister command (send "unregister YourEmailAddressHere" to [EMAIL PROTECTED])