This is a useful table that I'll have to look at more closely, but it wouldn't have predicted or prevented a problem I've had.

I recently had my home-grown[0] backup system fail silently because although the EXT4 formatted drive had bags of space remaining[1], it ran out of i-nodes.

That was ... unexpected.

Is there a suitable file system that doesn't have that problem?

[0] I have specific and complex requirements not met by any system I found, so despite the obvious potential pitfalls, rolling my own that did exactly and only what I wanted was a reasonable holding strategy.

[1] The system monitors all sorts of things and emails me warnings.

how many i-nodes were configured?

Now, after appropriate culls of the backups:

    $ df -i /dev/sdb1
    Filesystem        Inodes     IUsed    IFree IUse% Mounted on
    /dev/sdb1      152616960 101081254 51535706   67% /media/user/BackupA

So 152M Inodes ... it was the default when I formatted the drive.

    $ df -h /dev/sdb1
    Filesystem      Size  Used Avail Use% Mounted on
    /dev/sdb1       4.6T  1.4T  2.9T  33% /media/user/BackupA

Because Hans Reiser, who authored Reiser4 and ReiserFS, was later convicted of murdering his wife.

thats unfortunate...