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Re: XFS journaling position

To: xfs@xxxxxxxxxxx
Subject: Re: XFS journaling position
From: Robert Brockway <robert@xxxxxxxxxxxxxxxxx>
Date: Wed, 27 Oct 2010 10:27:32 -0400 (EDT)
In-reply-to: <201010270027.26687@xxxxxx>
References: <31c7e56286d37870011c17ee8e002760.squirrel@xxxxxxxxxxxxxxxxxxxx> <20101025161052.GC19425@xxxxxxx> <201010270027.26687@xxxxxx>
User-agent: Alpine 1.10 (DEB 962 2008-03-14)
On Wed, 27 Oct 2010, Michael Monnerie wrote:

in an area where disks are slower than on the outside. And if you fill
only half of the partition, it means your log is totally on the end of
the disk, access-wise.

Hi Michael.  Ignoring LVM for a moment...

My understanding is that the relationship between the physical cylinders and the logical cylinders software see is no longer necessarily linear - ie, the lower number logical cylinders aren't necessarily at the outer edge.

This article talks about this:

http://lissot.net/partition/mapping.html

Unless you know the underlying physical cylinder layout you can't reliably position the journal in the middle cylinder on the physical media.

I understand the disk drive manufacters aren't necessarily forthcoming with the necessary information although it could be established from timing tests.

Cheers,

Rob

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