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Re: xfs_growfs / planned resize / performance impact

To: Eric Sandeen <sandeen@xxxxxxxxxxx>
Subject: Re: xfs_growfs / planned resize / performance impact
From: Stefan Priebe - Profihost AG <s.priebe@xxxxxxxxxxxx>
Date: Fri, 03 Aug 2012 08:09:08 +0200
Cc: "xfs@xxxxxxxxxxx" <xfs@xxxxxxxxxxx>
In-reply-to: <501B4D7E.1000303@xxxxxxxxxxx>
References: <5017E426.2040709@xxxxxxxxxxxx> <501B4D7E.1000303@xxxxxxxxxxx>
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:14.0) Gecko/20120714 Thunderbird/14.0
Am 03.08.2012 06:03, schrieb Eric Sandeen:
On 7/31/12 8:56 AM, Stefan Priebe - Profihost AG wrote:
Hello list,

i'm planning to create a couple of VMs with just 30GB of space while using xfs 
as the main filesystem.

Now i alreay know that some of the VMs will grow up to 250GB while resizing the 
block device and using xfs_growfs.

Should i take care of that and format these disks with special parameters?

I've discovered that a 500GB volume has agcount=4 and 64000 blocks of internal 
log - while a 300GB volume resized to 500GB has agcount 7 ad only 40960 blocks 
of internal log.

Is it a problem if this grow will happen in small portions (30GB => 50GB => 75GB 
=> 100GB => ... 300GB)?

This incremental part doesn't matter a bit.  The first mkfs will choose the AG 
count & size according to defaults;
> further growth after this will add new (possibly partial) AGs of that pre-chosen size.

OK thanks for your reply. But does this influence performance? Should i perhaps start creating the 30GB with agcount 1 so that while raising the disk i don't end up with such a high agcount value? Does it make sense to create a bigger internal log from he beginning?



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