[Lustre-discuss] explanation about inodes in MDT/OST

[E.S. Rosenberg]

"
In a Lustre ldiskfs file system, all the inodes are allocated on the
MDT and OSTs when the file system is first formatted. The total number
of inodes on a formatted MDT or OST cannot be easily changed, although
it is possible to add OSTs with additional space and corresponding
inodes. Thus, the number of inodes created at format time should be
generous enough to anticipate future expansion.
"
http://build.whamcloud.com/job/lustre-manual/lastSuccessfulBuild/artifact/lustre_manual.xhtml#understandinglustre.fig.cluster

I am not sure I understand this 100%, when adding an OST I do or don't
gain inodes?or you basically only get more inodes in the data part of
the filesystem but if you don't have enough inodes on the MDT you
still have a problem?

Also if lustrefs is really based on ext4 doesn't ext4 support growing
the amount of inodes with resize2fs?

Thanks,
Eli