From: John Robinson <john.robinson@anonymous.org.uk>
To: Jiri Horky <jiri.horky@cesnet.cz>
Cc: Erwan MAS <erwan@mas.nom.fr>, Caspar Smit <c.smit@truebit.nl>,
linux-raid@vger.kernel.org, fio@vger.kernel.org
Subject: Re: Striping does not increase performance.
Date: Mon, 12 Mar 2012 16:23:21 +0000 [thread overview]
Message-ID: <4F5E22F9.1040208@anonymous.org.uk> (raw)
In-Reply-To: <4F5E0963.6080708@cesnet.cz>
On 12/03/2012 14:34, Jiri Horky wrote:
> Hi,
>
> as for alignment, please also check md metadata format version (-e
> switch of mdadm). The version that ensures alignment is 1.0, which
> places the metadata information to the back of the drive.
As far as I can tell from looking at the source, ever since the 1.x
metadata types were introduced (with mdadm 2.0, in August 2005):
* the data offset on 1.1 and 1.2 arrays has always been 4K-aligned,
* the superblock offset for 1.0 arrays has always been 4K-aligned,
* the bitmap offset for all 1.x arrays has always been 4K-aligned.
As of mdadm 3.1.2 (March 2010), the data offset for new 1.1 and 1.2
arrays is always 1MB (2048 sectors), so they're also 1M-aligned.
Cheers,
John.
next prev parent reply other threads:[~2012-03-12 16:39 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-03-12 12:34 Striping does not increase performance Caspar Smit
2012-03-12 12:57 ` Erwan MAS
2012-03-12 13:02 ` Caspar Smit
2012-03-12 13:02 ` Caspar Smit
2012-03-12 13:58 ` Erwan MAS
2012-03-12 14:34 ` Jiri Horky
2012-03-12 16:23 ` John Robinson [this message]
2012-03-12 14:33 ` Peter Grandi
2012-03-13 11:44 ` Caspar Smit
2012-03-12 14:20 ` David Brown
2012-03-13 11:55 ` Caspar Smit
2012-03-13 14:12 ` David Brown
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