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Re: xfs_growfs / planned resize / performance impact

To: stan@xxxxxxxxxxxxxxxxx
Subject: Re: xfs_growfs / planned resize / performance impact
From: Martin Steigerwald <Martin@xxxxxxxxxxxx>
Date: Sun, 5 Aug 2012 15:49:22 +0200
Cc: xfs@xxxxxxxxxxx, Eric Sandeen <sandeen@xxxxxxxxxxx>, "Stefan Priebe - Profihost AG" <s.priebe@xxxxxxxxxxxx>
In-reply-to: <501E6872.6000503@xxxxxxxxxxxxxxxxx>
References: <5017E426.2040709@xxxxxxxxxxxx> <201208051303.09337.Martin@xxxxxxxxxxxx> <501E6872.6000503@xxxxxxxxxxxxxxxxx> (sfid-20120805_153826_573731_00E594B5)
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Am Sonntag, 5. August 2012 schrieb Stan Hoeppner:
> On 8/5/2012 6:03 AM, Martin Steigerwald wrote:
> > Well the default was 16 AGs for volumes < 2 TiB AFAIR. And it has
> > been reduced to 4 for as I remember exactly performance reasons. Too
> > many AGs on a single device can incur too much parallelity. Thats at
> > least is what I have understood back then.
> For striped md/RAID or LVM volumes mkfs.xfs will create 16 AGs by
> default because it reads the configuration and finds a striped volume.
> The theory here is that more AGs offers better performance in the
> average case on a striped volume.
> With hardware RAID or a single drive, or any storage configuration for
> which mkfs.xfs is unable to query the parameters, mkfs.xfs creates 4
> AGs by default.  The 4 AG default has been with us for a very long
> time.  It was never reduced.

That does not match my memory, but I´d have to look it up. Maybe next 

I am pretty sure mkfs.xfs on a single partition on a single harddisk upto 
2 TiB used 16 AGs for quite some time and now uses 4 AGs since quite some 
time already. I think I have noted the exact xfsprogs version where it was 
changed in my training slides.

Martin 'Helios' Steigerwald - http://www.Lichtvoll.de
GPG: 03B0 0D6C 0040 0710 4AFA  B82F 991B EAAC A599 84C7

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