flyusa2010 fly wrote: > Thanks for your reply. > Yes, i mean disk may lie to os.
Our documentation covers this extensively: http://www.postgresql.org/docs/9.0/static/wal-reliability.html --------------------------------------------------------------------------- > > > On Fri, Dec 3, 2010 at 12:14 PM, Stefan Kaltenbrunner > <ste...@kaltenbrunner.cc> wrote: > > > On 12/03/2010 06:43 PM, Heikki Linnakangas wrote: > > > >> On 03.12.2010 13:49, flyusa2010 fly wrote: > >> > >>> When writing log, dbms should synchronously flush log to disk. I'm > >>> wondering, if it is possible that the logs are in disk cache, while the > >>> control is returned to dbms again, so dbms thinks logs are persistent on > >>> disk. In this case, if the disk fails, then there's incorrectness for > >>> dbms > >>> log writing, because the log is not persistent, but dbms considers it is > >>> persistent! > >>> > >> > >> I have no idea what you mean. The method we use to flush the WAL to disk > >> should not be fallible to such failures, we wait for fsync() or > >> fdatasync() to return before we assume the logs are safely on disk. If > >> you can elaborate what you mean by "control is returned to dbms", maybe > >> someone can explain why in more detail. > >> > > > > I think he is refering to the plain old "the disk/os is lying about whether > > the data really made it to stable storage" issue(especially with the huge > > local caches on modern disks) - if you have such a disk and/or an OS with > > broken barrier support you are doomed. > > > > > > Stefan > > -- Bruce Momjian <br...@momjian.us> http://momjian.us EnterpriseDB http://enterprisedb.com + It's impossible for everything to be true. + -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers