For my dual-boot laptop, I have bought a large hard drive to use as external USB solution. I decided to use EXT3 as filesystem, thinking to use Ext2IFS to access the drive from Windows (as I already do with various other external devices).
Linux is my primary choice as OS; as such, the drive was already 2/3rd full before I ever attempted to access it from Windows. It was only then I realized I made a severe mistake - I forgot to limit the inode size to 128. The default value used by the Linux distro was 256, which Ext2IFS cannot access.
At 1 TB, the drive is by far my largest storage, and at 2/3rd full would be awkward to backup.
Is it possible to change the inode size on an EXT3 partition (without losing the data)? I don't care if it takes a couple of hours.
David Spillett perfectly answered the original question - "how to change the inode size on an EXT3 partition?".
The underlying question, however, was "how do I access an EXT3 partition from Windows after I created it with the Linux default values for inode size?".
The answer would be Ext2Fsd, which is an EXT3 driver for Windows that doesn't balk at large inode sizes. (It does not, however, support GUID Partition Tables (GPT), required for drives larger than 2 TB.)
I thought this might be of interest for the many people who look at this question.