On 10/25/11 14:03, Adriano dos Santos Fernandes wrote:
> On 25/10/2011 07:56, Paul Reeves wrote:
>> On Tuesday 25 October 2011 at 11:12 marius adrian popa wrote:
>>
>>> In other words: if you use Ext3 and you note performance regressions
>>> with this release, try disabling barriers ("barriers=0" mount option).
>> I can understand doing this for routine desktop work. It does make a
>> difference. But for a database server? The problem is that the old behaviour
>> was the wrong behaviour. Letting the hard drive re-order page writes
>> completely negates the efforts firebird makes to ensure pages are written in
>> the correct order.
>>
>>
> Let consider ext3/4 filesystem with barriers enabled, then:
>
> 1) FW=ON - each page written by Firebird goes to disk immediately, in
> the order issued by Firebird
> 2) FW=OFF, and use fsync on COMMIT - pages will not be reordered, and
> when COMMIT happens they will be written to disk in order
>
> Is this wrong? What's then the advantage of (1), since it's much slower
> approach?
If fsync() is done not on commit, but each time we finish with the group
of dependent pages (there may be >1 group on commit) - yes, this will
work provided fsync() issues HW barriers.
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