[Beowulf] LSI Megaraid stalls system on very high IO?

[Skylar Thompson]

On 08/04/2014 01:24 AM, John Hearns wrote:
> Mark, you are of course correct.
> Flush often and flush early!
> 
> As an aside, working with desktop systems with larger amounts of memory
> I would adjust the 'swappiness' tunable
> and also the min_free_kbytes.
> Min_free_kbytes in Linux  is by default set very low for modern high
> memory systems.
> I had systems with 128Gbytes of RAM which would lock up in a similar
> fashion as you describe. Setting higher min_free_kbytes helped with the
> 'system paging itself into the deck' type of behaviour.
> See:
> https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/6/html/Performance_Tuning_Guide/s-memory-tunables.html

Agreed, and even more so when you have systems with hundreds of
gigabytes of RAM whose dirty buffers are backed by a single NFS server
with a fraction of that RAM for write cache.

Skylar