[Pw_forum] Further reduce disk IO for ph.x

[Yao Yao]

On Fri, 7 Dec 2012 05:28:54 PM Paolo Giannozzi wrote:
> there are many files, not a single one. They are all written into a
> subdirectory of "outdir"/"prefix".save
Thank you. I will make that folder a link to another folder in /dev/shm.
> it is definitely possible, but it requires some programming work. The
> code "as is" uses a lot of disk space. Note however that modern
> operating systems tend to keep files into RAM as much as possible,
> so if you have enough RAM. it may not make such a big difference
> whether you keep things into RAM or if you write them to file.
I also thought it should be cached well in memory. But thing didn't go as we 
expected. The cluster runs Rocks Linux. Each job runs on a 48-core 96GB 
diskless node. The job uses ~3GB meory only. The work directory is a remote 
filesystem (probably NFS). The network traffic is very high, this probably means 
the RAM caching is not working as expected, though I did see ~5GB RAM is used 
for cache. Maybe the caching policy is more restricted for shared filesystems 
like NFS.
-- 
Yao Yao
PhD. Candidate
3rd Generation Strand
ARC Photovoltaics Centre of Excellence
University of New South Wales
Sydney, NSW Australia