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:
+ 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.
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.
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