IBM Spectrum Scale Sharing Nothing Cluster performance tuning guide has been posted and please refer to link before you doing the below change.
Database workload customers using direct I/O must also enable the following preStealPct tuning if they are running any of the following Spectrum Scale levels: 3.5 (any PTF level), 4.1.1 (below PTF 10), 4.2.0 (any PTF level), or 4.2.1 (below PTF 2). These database workload customers with direct I/O enabled running these older code levels must tune preStealPct as follows:
echo 999 | mmchconfig preStealPct=0 -i
After upgrading to IBM Spectrum Scale from one of the previously referenced older code levels to a higher level, especially (4.1.1 PTF 10, 4.2.1 PTF 2, or 188.8.131.52 or higher, you can set the configuration option ‘preStealPct=0’ back to its default value as follows:
echo 999 | mmchconfig preStealPct=1 -i