On Tue, 2007-07-24 at 10:51 +0200, Florian Weimer wrote:
> +    <para>
> +     Asynchronous commit provides different behaviour to setting 
> +     <varname>fsync</varname> = off, which is a server-wide
> +     setting that will alter the behaviour of all transactions,
> +     overriding the setting of <varname>synchronous_commit</varname>,
> +     as well as risking much wider data loss.  With <varname>fsync</varname> 
> +     = off the WAL written but not fsynced, so data is lost only in case
> +     of a system crash. Both WAL and datafiles written within the last 
> +     few seconds would be at risk, affecting all types of database 
> +     transactions. The precise number depends upon whether your operating 
> +     system is configured for automatic filesystem writeback and what the 
> +     delay is set too; Linux currently defaults to 30 seconds.  With 
> +     asynchronous commit the WAL is not written to disk at all at commit 
> +     time, so data is lost if there is a database server crash, whether or
> +     not the system crashes at the same time.
> +    </para>
> I think fsync=off also endagers metadata, while synchronous_commit=off
> should be perfectly safe as far as the metadata is concerned.
> Wouldn't this be worth mentioning as well?

Well, I think "wider data loss" covers it for me, but I don't have a
problem with people wanting to detail the various problems that can

  Simon Riggs
  EnterpriseDB  http://www.enterprisedb.com

---------------------------(end of broadcast)---------------------------
TIP 1: if posting/reading through Usenet, please send an appropriate
       subscribe-nomail command to [EMAIL PROTECTED] so that your
       message can get through to the mailing list cleanly

Reply via email to