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Re: regarding the inode64 mount option

To: Michael Weissenbacher <mw@xxxxxxxxxxxx>
Subject: Re: regarding the inode64 mount option
From: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Date: Thu, 28 May 2009 10:56:15 -0400
Cc: xfs@xxxxxxxxxxx
In-reply-to: <4A1E81D8.7010706@xxxxxxxxxxxx>
References: <4A1E81D8.7010706@xxxxxxxxxxxx>
User-agent: Mutt/1.5.18 (2008-05-17)
On Thu, May 28, 2009 at 02:21:44PM +0200, Michael Weissenbacher wrote:
> Hi XFS-List!
> I understand that the inode64 mount option allows inodes to be created beyond 
> 1TB. There are also certain performance problems that can be cured by using 
> this option when handling LOTS of inodes. During my tests i noticed that 
> enabling it is like a one-way street. Inodes created with inode64 enabled 
> aren't accessible when the option is left out.

Actually they should still be accessible, we just won't create new
inodes not addressable by 32bit inode numbers.

> Now i got a few questions:
> - Does the inode64 option work only on 64bit architectures or is it also 
> possible to use it with i686

It is available for 32bit kernels starting with kernel 2.6.29.

> - Is there a way to convert the inodes back

There's an xfs_reno tool ported from IRIX to renumber the inodes.  I'll
see if I can finally get it packaged.

> - Why doesn't the filesystem remember that inode64 was used in the past and 
> enable it automatically

Good question.  We could introduce a flag in the superblock for this.

> - Do i have to pass inode64 via grub / lilo if i want to use it on my root 
> filesystem

Yes.

> I haven't found any definitive clear documentation abount the pro's and 
> con's, so maybe you can give me some hints :-)

The only reason speaking against inode64 are old buggy programs that
can't cope with a 64bit ino_t, Eric had a quite scary list of those
in Fedora somewhere..

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