If Samba has been built with asynchronous I/O support and this integer parameter is set to non-zero value, Samba will write to file asynchronously when size of request is bigger than this value. Note that it happens only for non-chained and non-chaining reads and when not using write cache. Current implementation of asynchronous I/O in Samba 3.0 does support only up to 10 outstanding asynchronous requests, read and write combined. write cache size aio read size 0 16384 Use asynchronous I/O for writes bigger than 16KB request size