Re: Is it possible to change sunit of log section post-mkfs

From: Michael Weissenbacher <mw@dermichi.com>
To: Dave Chinner <david@fromorbit.com>
Cc: xfs@oss.sgi.com
Subject: Re: Is it possible to change sunit of log section post-mkfs
Date: Tue, 3 Nov 2015 20:32:14 +0100	[thread overview]
Message-ID: <56390BBE.6030102@dermichi.com> (raw)
In-Reply-To: <20151103191132.GD19199@dastard>

Hi Dave!

>>
>> What i want to achieve is to set the log sunit to the maximum possible
>> of 64 blks (=256KiB).
On 2015-11-03 20:11, Dave Chinner wrote:
> 
> Why? Is there a performance problem with the default setting?
> 
I am seeing very bad performance of "rm" on this file system. Of course
I know that RAID-6 is kind of a worst case setup for that workload. But
I was hoping that aligning the log correctly plus increasing the stripe
size would help. Wouldn't the file system write more of the log at once
with a bigger sunit size; resulting in fewer RMW cycles?

I am already using delaylog, inode64, nobarrier to mount the fs;
lazy-count=1.

Maybe moving to an external log would be the best option?

tia,
Michael

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