[Gllug] Painfully slow MySql performance on 64-bit Atom processor

Richard Huxton dev at archonet.com
Wed Jan 19 09:30:32 UTC 2011

On 18/01/11 19:52, John Winters wrote:
> I've since done some more reading and the essential difference
> apparently is that ext3 defaults to "barrier=0" and ext4 defaults to
> "barrier=1". Still not quite sure what it means though.

This is enabling "write barriers". Writes before a barrier is guaranteed 
to be written to real, magnetic physical disk before writes after it. 
Otherwise you can end up with a mix of multiple journal updates and 
file-block updates getting partially written to disk with a crash.


Contrary to what you might think, this is less useful for databases than 
other applications. RDBMs tend to handle their own transaction logs 
carefully anyway.

   Richard Huxton
   Archonet Ltd
Gllug mailing list  -  Gllug at gllug.org.uk

More information about the GLLUG mailing list