[Samba] ext4 failure on cluster

[steve]

Note: here is a post we sent to the openSUSE list which we'd like to
share here. Cheers.

Hi everyone
Next month we hope to go into production with our drbd-ocfs2-ctdb
cluster. Of course, we must prove to our boss that it is a fair if not
better replacement for our single AD domain file-server which it will
replace.

A few questions remain to which we cannot find a simple answer that a
non technical person would understand. Indeed, much of what we've read
we cannot understand ourselves as self styled ha setter-uppers:
1. Where our single ext4 file server is predictable under load (it just
gets slower), with both nodes up, why does the cluster fail so badly
under ext4 but absolutely screams under ocfs2? The strange thing is that
the clustered ext4 actually performs better when only one node is up.
2. Following what is happening with vbox and mysql, are Oracle likely to
re-licence ocfs2 in the same way any time soon?
3. IF (2), do openSUSE or anyone else plan a fork (thinking e.g.
mariadb)?

General chit-chat/verbose/historical answers especially welcome.

Thanks,
L & S pp all the Linux team here in Alicante.