linux-kernel - Re: [noob q. on block layer] block IO read-ahead during sequential *write*?

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Message-ID: <4782588A.3856.1B9C57D9@localhost>
Date:	Mon, 07 Jan 2008 16:51:22 +0100
From:	"Frantisek Rysanek" <Frantisek.Rysanek@...t.cz>
To:	"Jörn Engel" <joern@...fs.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [noob q. on block layer] block IO read-ahead during sequential *write*?

On 7 Jan 2008 at 13:49, Jörn Engel wrote:
>
> If you retry the dd with bs=4096 (or whatever your architecture's page
> size happens to be), does this still occur?
> 
> JĂśrn
> 
wow, thanks, it works, this is so obvious.
I tend to use values like bs=512000 or suchlike, but probably never
stroke this particular value when I was looking at iostat.
Must've missed that modulo 4096 somehow.

Seems like cp is using 512B per transaction, judging by how slow the
transfer goes. If I use bs=500000 or even bs=1024, it goes faster.

Have a nice day :-}

Frank Rysanek
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