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

Nix nix at esperi.org.uk
Fri Jan 21 22:03:29 UTC 2011

On 19 Jan 2011, Richard Huxton outgrape:

> 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.

Yeah. Only turn on nobarrier if you don't mind metadata loss after
crashes (i.e. possibly losing whole directories, although that is quite
unlikely) or if you have a battery-backed disk controller (the cheapest
of these is called a 'laptop').
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