Lustre 1.6 Operations Manual

What does "denying connection for new client" mean?
When service nodes are performing recovery after a failure, only clients which were
connected before the failure are allowed to connect. This enables the cluster to first
re-establish its pre-failure state, before normal operation continues and new clients
are allowed to connect.
How do I set a default debug level for clients?
If using zeroconf (mount -t lustre), you can add a line similar to the following to
your modules.conf:
post-install portals sysctl -w lnet.debug=0x3f0400
This sets the debug level, whenever the portals module is loaded, to whatever value
you specify. The value specified above is a good starting choice, and will become the
in-code default in Lustre 1.0.2, as it provides useful information for diagnosing
problems without materially impairing the performance of Lustre.)
How can I improve Lustre metadata performance when using large
directories (> 0.5 million files)?
On the MDS, more memory translates into bigger caches and, therefore, higher
performance. One of the requirements for higher metadata performance is to have
lots of RAM on the MDS.
The other requirement (if not running a 64-bit kernel) is to patch the core kernel on
the MDS with the
3G/1G patch to increase the available kernel address space. This, again, translates
into having support for bigger caches on the MDS.
Usually the address space is split in a 3:1 ratio (3G for userspace and 1G for kernel).
The 3G/1G patch changes this ratio to 3G for kernel/1G for user (3:1) or 2G for
kernel and 2G for user (2:2).
Appendix D Lustre Knowledge Base D-5