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Re: What is a recommended XFS sector size for hybrid (512e) advanced for

To: Stan Hoeppner <stan@xxxxxxxxxxxxxxxxx>
Subject: Re: What is a recommended XFS sector size for hybrid (512e) advanced format hard drives?
From: Matthias Schniedermeyer <ms@xxxxxxx>
Date: Tue, 6 Jan 2015 09:35:07 +0100
Cc: Hillel Lubman <shtetldik@xxxxxxxxx>, xfs@xxxxxxxxxxx
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <54AA0A93.2010204@xxxxxxxxxxxxxxxxx>
References: <1806495.BCZcrVVEOf@shtub-cm> <54AA0A93.2010204@xxxxxxxxxxxxxxxxx>
User-agent: Mutt/1.5.23 (2014-03-12)
On 04.01.2015 21:52, Stan Hoeppner wrote:
> On 01/04/2015 06:56 PM, Hillel Lubman wrote:
> ...
> > Looking around I saw some references that it's preferable to use sector
> > size (sectsz) of 4 KB when creating XFS partitions on hybrid (512e)
> > advanced format hard drives and also some mentions of making that a
> > default in mkfs.xfs. However I noticed that my current mkfs.xfs (3.2.1)
> > used with current Debian testing (Linux 3.16.0) still uses 512 B sectors
> > by default.
> ...
> > Can you please clarify what after all is the recommended sector size for
> > such drives and why isn't it a default in mkfs.xfs (since supposedly
> > defaults are generally recommended optimal settings unless you have some
> > special use case).
> ...
> 
> XFS sectsz is unimportant with these drives.  What matters is that any
> partitions you create start and end on 4KB boundaries.  This will
> prevent adjacent hardware sector RMW internal to the drive.  XFS writes
> in 4KB filesystem blocks on Linux.  As long as the fsblocks are aligned
> to the 4KB hardware sectors there's nothing more you can do to avoid
> performance penalties with these drives.

Not in my experience. My first (and lying about it) AF HDD had horrible 
write performance until i re'mkfs.xfs'ed it with 4k sector-size. And yes 
the aligned was 4k.

But that was many years ago and i don't know if newer XFS (IIRC that was 
before delay-log) would behave better. But as all of my storage after 
the first AF HDD was either an AF HDD or a SSD i have been formating 
everything with 4k sector-size for years.




-- 

Matthias

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