FC5: "ext_attr" and "large_file" features for ext3 file systems ???

Stephen C. Tweedie sct at redhat.com
Mon Apr 3 20:06:58 UTC 2006


Hi,

On Tue, 2006-03-28 at 13:52 -0800, Robinson Tiemuqinke wrote:

>  First, what's the "large_file" feature REALLY means?
> Then, what's the size of "large file" to light this
> feature on? 2GB, or 2TB? 

2GB.

>  Second, the "ext_attr" feature seems another
> automatic one: it only appears after the first
> "setfacl" command runs on the file system and then the
> feature will keep on there forever even ACL is
> removed. What's the indication of "ext_attr" feature
> and what are the reasons behind to have this feature?

They are there simply to indicate that a given feature is present on the
filesystem.  They prevent old versions of the kernel and/or e2fsck tools
from mistakenly operating on a filesystem with newer features,
potentially corrupting things on disk or returning incorrect file
contents.

All remotely recent kernels have large file support for ext3, and all
2.6 ones (and many vendor-supplied 2.4 ones) have ext_attr, so you have
to be running something pretty old to run into compatibility problems
with either of those features.

--Stephen





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