Hi, Probably, we may be able to use the following formula to calculate the maximum number of CIOD_RDWR_BUFFER_SIZE. CIOD_RDWR_BUFFER_SIZE_max = (MemTotal-MemSysUsed)/(2*N) where, MemTotal : total installed memory MemSysUsed : memory used by system software N : the number of compute nodes per one I/O node. (PSET) The reason why we need (2*N) is that we have to think about the virtual mode. MemTotal is 512MByte per default( no exception?). ZeptoOS1.1 uses approx. 60MB which includes pvfs2, sshd, etc memory usage. On the most of BGL systems, PSET is 32 and CIOD_RDWR_BUFFER_SIZE_max is going to be approx. 7 MBytes. PSET is available from /proc/personality.sh, so we could automatically calculate the max size during ION boot-time. If something wrong, please correct me. Thanks, Kaz