Thanks Jens, but why when we run READS only (not mixed) we don't have performance issues? (We run with direct=0)?

----- Original Message -----
From: Jens Axboe <axboe@kernel.dk>
To: Neto, Antonio Jose Rodrigues
Cc: zhu.yanhai@gmail.com <zhu.yanhai@gmail.com>; Rettl, Matthias; fio@vger.kernel.org <fio@vger.kernel.org>
Sent: Fri Sep 02 20:09:26 2011
Subject: Re: Bad performance when reads and writes on same LUN

On 2011-09-02 21:06, Neto, Antonio Jose Rodrigues wrote:
> The question that I have is:
> 
> "Buffered aio will fall back to sync io, and it's known that mixing"
> 
> Why did buffered aio will fall back to sync io?

Please don't top post, reply beneat the original text.

Buffered aio will degenerate to normal sync IO, because the kernel does
not support async buffered io.

-- 
Jens Axboe