Re: WAL documentation changes

Josh Berkus wrote:
> 
> >> First, none of the general purpose filesystems I've seen so far do data
> >> journalling per default, since it's a huge performance penalty, even for
> >> non-RDBMS workloads. The feature you talk about is ext3 specific (and
> >> should be pointed out as such) and only disables write ordering, meaning
> >> that metadata and file content updates are not synchronized.
> > 
> > You are right that my docs were misleading.  I have improved them by
> > mentioning that it is _data_ flush that as part of journalling that can
> > be a problem, and documented that the mount option listed is
> > ext3-specific, not linux-specific.
> 
> Actually, I think that some of the other journalling filesystems allow 
> data journalling (I know ReiserFS does), they just don't default to it. 
>   For that matter, a few (ZFS in particular) have data journalling which 
> can't be turned off.  While it's not a tuning parameter, users should be 
> warned that they'll take a performance hit from it.

So I assume you are saying the docs are fine now.

--  Bruce Momjian  <bruce@momjian.us>        http://momjian.us EnterpriseDB
http://enterprisedb.com
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