[Lustre-discuss] noatime or atime_diff for Lustre 1.8.7?

[Mohr Jr, Richard Frank (Rick Mohr)]

On Dec 10, 2012, at 11:43 AM, Grigory Shamov wrote:

> I wonder how would be a best strategy to change the striping now. I understand that if I just change the stripe count on the Lustre root dir, it will affect only newly created files/directories. Should I copy the user's files, stripe their directories and then copy the data back? That sounds somewhat dangerous, especially if the users do some unusual things with symlinks..

In our case, we approached the problem with user training.  We didn't make any changes to the file system itself.

In general, these users had small to medium files so we wanted them to use stripe count 1 for their files.  The primary exception was for these shared input files that were hit hard by multiple readers.  We contacted the users, explained the situation, and gave them pointers on using "lfs setstripe".  Once they started running jobs and seeing 30+% speed up, they were happy to manage the striping for their files.

I don't know your situation, so I can't say if that approach would work for you.  My experience has been that no matter what you choose for the default stripe count, someone will create files that don't work well with the default.  So there always seems to be some need for user education.

-- 
Rick Mohr
Senior HPC System Administrator
National Institute for Computational Sciences
http://www.nics.tennessee.edu