NERSCPowering Scientific Discovery Since 1974

Important notice about using /house

July 6, 2012

Description

There have been a lot of issues recently with NFS hangs on the gpint machines.
The origin of the gpint hanging has been determined to be a defect in the Isilon filesystem software, and happens when a file being written is simultaneously opened for reading on the same host.
 
This most frequently happens when people tail files being written by the same machine.
 
E.g.:  DO NOT DO THIS:
gpint17 $ ./somewritingProcess > outfile &
gpint17 $ tail -f outfile
 
This very common (and desirable) operation has been determined to hang the filesystem on the host reading/writing the file.  We are working with the vendor to try to correct this situation, but in the meantime a work-around is to read the file from a different machine than the writer:
 
E.g.: THIS IS OK
gpint17 $ ./somewritingProcess > outfile &
gpint17 $ ssh gpintXX
gpintXX $ tail -f outfile
 
Please note that these problems are not limited to the gpint machines - but any machine connected to /house.  Please write me back with any questions, and file tickets at http://help.nersc.gov if you run into any trouble.