Right now a partition can be configured to sync to disk on each write operation. This is a per partition configuration parameter. Then there is this system wide syncPeriodMillis parameter which can be set to sync up all the partitions on some interval specified. When 0 no sync requests to the core are made.
The question is does this system wide parameter bypass per partition syncOnWrite settings?
This solution really stinks because the configuration is spread across two parts of the server and the correlation is hard to grasp because of this. Eventually we need to centralize the schedular service (Quartz) to have each partition register for cyclic triggers that allow it to sync up writes periodically if that is preferred. Otherwise it syncs when each write occurs. We can thus get ride of this syncOnWrite attribute for partitions and just have a syncMillis parameter. If set to 0 then syncs occur on each write. If set to some interval then writes to disk will be cached.