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Re: SQLite and ext3 journalling mode



On 12/08/2010 02:02 PM, Miller, Mike (OS Dev) wrote:

-----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



Right - upstream has been working to make sure that we can default to barriers on and not see a performance hit for devices like arrays that don't need them ...

Ric


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