Am Dienstag, 17. Juli 2007 20:31 schrieb Simon Riggs: > Here's the latest version. I've reviewed this to check that this does > what I want it to do, re-written various comments and changed a few > minor points in the code. > > I've also added a chunk to transam/README that describes the workings of > the patch from a high level. > > Now ready for final review.
I'm not sure the following explanation is all that clear: + <para> + Asynchronous commit provides different behaviour to setting + <varname>fsync</varname> = off, since that 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. With asynchronous commit the WAL is not written + to disk at all by the user, so data is lost if there is a database + server crash, as well as when the system crashes. + </para> On the one hand, it claims that fsync off has much wider data loss implications than asynchronous commit, on the other hand, it states that the risk of a loss due to asynchronous commit happening is larger than fsync off. I *think* I know what this is trying to say, but I suspect that the average user might not be able to make a good choice of settings. -- Peter Eisentraut http://developer.postgresql.org/~petere/ ---------------------------(end of broadcast)--------------------------- TIP 5: don't forget to increase your free space map settings