Filesystem won't mount because of "unsupported optional features (80)"

Andreas Dilger adilger at
Sat Feb 17 07:28:27 UTC 2007

On Feb 17, 2007  01:32 -0500, Maurice Volaski wrote:
> I made a filesystem (mke2fs -j) on a logical volume under kernel 
> 2.6.20 on a 64-bit based system, and when I try to mount it, ext3 
> complains with
> EXT3-fs: dm-1: couldn't mount because of unsupported optional features (80).
> I first thought I just forgot to make the filesystem, so I remade it 
> and the error is still present. I ran fsck on this freshly made 
> filesystem, and it completed with no errors.
> Filesystem features:      has_journal resize_inode dir_index filetype 
>			    64bit sparse_super large_file

> What could be causing this error and what does "80" refer to?

For some reason the 64bit feature is set in the filesystem.  This should
only be set for ext4dev filesystems.  Are you specifying this feature
yourself e.g. "mke2fs -O 64bit ..."?  Your filesystem is only 2.7TB so
you don't need the 64bit feature set and it doesn't really help you
unless you plan to expand the logical volume past 16TB.

If you do need this functionality then you need to use the ext4dev
filesystem, but this is currently a work-in-progress and shouldn't
be used for critical data.

Cheers, Andreas
Andreas Dilger
Principal Software Engineer
Cluster File Systems, Inc.

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