[gentoo-user] ext4 inline data

[gentoo-user] ext4 inline data

[Florian Philipp]

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Hi list!

I noticed that beginning with kernel 3.8, ext4 can store small files
entirely inside the inode. But I couldn't find much additional information:

- Is the improvement automatically enabled?

- Is the change backwards compatible? Can I still read such files with
kernel 3.7?

- Can current stable e2fsprogs (especially e2fsck) handle this?

Thanks in advance!
Florian Philipp


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Re: [gentoo-user] ext4 inline data

[Paul Hartman]

On Fri, Mar 29, 2013 at 8:48 AM, Florian Philipp <lists@binarywings.net> wrote:
> Hi list!
>
> I noticed that beginning with kernel 3.8, ext4 can store small files
> entirely inside the inode. But I couldn't find much additional information:
>
> - Is the improvement automatically enabled?

I don't believe so. I think you need to explicitly enable the feature
inline_data when you mkfs.

> - Is the change backwards compatible? Can I still read such files with
> kernel 3.7?

It is defined as INCOMPAT_INLINE_DATA so an older kernel should refuse
to mount it at all if it does not know how to handle this option.

Depending on your partition layout, you may also need a boot loader
which knows how to read inline data. I think there is a patch to
enable it on grub2, not sure if it is included in mainline or not.

> - Can current stable e2fsprogs (especially e2fsck) handle this?

I grepped sources of e2fsprogs 1.42.7 and it contains references to
inline data, but manpages don't. mkfs looks like it might not support
the inline_data option yet? So I'm not sure if things are quite ready
for "prime time"... If you try, please let us know how it goes. :)

Re: [gentoo-user] ext4 inline data

[Pandu Poluan]

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On Mar 29, 2013 8:49 PM, "Florian Philipp" <lists@binarywings.net> wrote:
>
> Hi list!
>
> I noticed that beginning with kernel 3.8, ext4 can store small files
> entirely inside the inode. But I couldn't find much additional
information:
>
> - Is the improvement automatically enabled?
>
> - Is the change backwards compatible? Can I still read such files with
> kernel 3.7?
>
> - Can current stable e2fsprogs (especially e2fsck) handle this?
>
> Thanks in advance!
> Florian Philipp
>

My question would be: Will it introduce a significant advantage to my
situation, so much so that I'm willing to live with the obvious drawbacks?

Rgds,
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Re: [gentoo-user] ext4 inline data

[Paul Hartman]

On Fri, Mar 29, 2013 at 2:20 PM, Pandu Poluan <pandu@poluan.info> wrote:
> My question would be: Will it introduce a significant advantage to my
> situation, so much so that I'm willing to live with the obvious drawbacks?

Here are some benchmarks:

http://permalink.gmane.org/gmane.comp.file-systems.ext4/34290