[lustre-discuss] Lustre caching and NUMA nodes

[Peter Grandi]

> I have a an OSC caching question.  I am running a dd process
> which writes an 8GB file.  The file is on lustre, striped
> 8x1M.

How the Lustre instance servers store the data may not have a
huge influence on what happens in the client's system buffer
cache.

> This is run on a system that has 2 NUMA nodes (  cpu sockets).
> [...] Why does lustre go to the trouble of dumping node1 and
> then not use node1's memory, when there was always plenty of
> free memory on node0?

What makes you think "lustre" is doing that?

Are you aware of the values of the flusher settings such as
'dirty_bytes', 'dirty_ratio', 'dirty_expire_centisecs'?

Have you considered looking at NUMA policies e.g. as described
in 'man numactl'?

Also while you surely know better I usually try to avoid
buffering large amounts of to-be-written data in RAM (whether on
the OSC or the OSS), and to my taste 8GiB "in-flight" is large.