From: | Doug McNaught <doug(at)mcnaught(dot)org> |
---|---|
To: | Shane Wright <shane(dot)wright(at)edigitalresearch(dot)com> |
Cc: | pgsql-general(at)postgresql(dot)org |
Subject: | Re: mount -o async - is it safe? |
Date: | 2006-01-19 12:51:55 |
Message-ID: | 87ek34v0r8.fsf@asmodeus.mcnaught.org |
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Lists: | pgsql-general |
Martijn van Oosterhout <kleptog(at)svana(dot)org> writes:
> That depends. As long as the data is appropriately sync()ed when
> PostgreSQL asks, it should be fine. However, from reading the manpage
> it's not clear if fsync() still works when mounted -o async.
>
> If -o async means "all I/O is asyncronous except stuff explicitly
> fsync()ed" you're fine. Otherwise...
That's the way it works. Async is the default setting for most
filesystems, but fsync() is always honored, at last as far as
non-lying hardware will allow. :)
> The usual advice is to stick the WAL on a properly synced partition and
> stick the rest somewhere else. Note, I have no experience with this,
> it's just what I've heard.
This might not be optimal, as having every write synchronous actually
results in more synced writes than are strictly necessary.
-Doug
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