The journalling file system saga

Peter Schuller peter.schuller at
Thu May 13 16:27:41 PDT 2004

> [Problems with softupdates]
> > Yet another problem is that an fsync() no longer guarantees that data is
> > on disk, even with write caching disabled on the media. This doesn't
> > break things like PostgreSQL provided that the order of writes is
> > preserved, but it does break things like MTA:s that want to guarantee
> > that critical data has been commited to persistent storage before
> > signaling success to an external entity (SMTP client).
> fsync(2) works as advertised with softupdates enabled so that shouldn't
> cause any problems for applications that are written properly.

Ah thanks! I was under the distinct impression that was not the case. This is 
indeed good news. I can now rest easy running PostgreSQL without disabling 
soft updates.

Perhaps a document would be in order describing/detailing all the details such 
as this about soft updates, all in one place. What I know I have mostly 
gathered by reading papers and random mailinglist postings about certain 
specifics. Is there such a thing in existence? If not I may try to put one 
together, for other people like me.

/ Peter Schuller, InfiDyne Technologies HB

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