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RE: SQLite and ext3 journalling mode




> -----Original Message-----
> From: ext3-users-bounces redhat com [mailto:ext3-users-
> bounces redhat com] On Behalf Of Ric Wheeler
> Sent: Wednesday, December 08, 2010 11:08 AM
> To: Richard Hipp
> Cc: ext3-users redhat com
> Subject: Re: SQLite and ext3 journalling mode
> 
> On 12/08/2010 11:56 AM, Richard Hipp wrote:
> >
> >
> > On Wed, Dec 8, 2010 at 11:25 AM, Ric Wheeler <ricwheeler gmail com
> > <mailto:ricwheeler gmail com>> wrote:
> >
> >     On 12/08/2010 06:52 AM, Dan Kennedy wrote:
> >
> >
> >         Thanks. But to be clear, is data=ordered better than
> data=writeback
> >         wrt. data integrity following a power failure?
> >
> >         Regards,
> >         Dan.
> >
> >
> >     Data integrity can mean a couple of different things.
> >
> >     If you are file system meta-data centric (i.e., a file system
> developer or
> >     just worried about having to run fsck after a crash to repair the
> file
> >     system), then both options *should* be equivalent.
> >
> >     If you are one of those annoying users who define data integrity
> to
> >     include those annoying details like will my file have garbage in
> it after
> >     a crash that will make my DB or other app puke, then data ordered
> is
> >     clearly more robust.
> >
> >
> > Thanks, Ric.  Yes, we are numbered among the "annoying users".  Based
> on what
> > you are telling us, we'll recommend that people use data=ordered,
> barrier=1

Just as an FYI, not all HW vendors enable the drive write cache especially on array controllers. In those cases barriers do nothing.

-- mikem

> > for maximum data reliability in the face of power loss.
> 
> That is what I do as well - there are use cases and users that prefer
> the lower
> latency and can accept the trade offs that come with data writeback or
> non-barrier use, but I certainly think most users would be better using
> the
> settings you have above.
> 
> Good luck!
> 
> Ric
> 
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