VERITAS File System 3.5 (HP OnlineJFS/JFS 3.5) Administrator's Guide (August 2003)

Chapter 2
VxFS Performance: Creating, Mounting, and Tuning File Systems
Choosing mount Command Options
33
Because the mincache=direct, mincache=unbuffered, and mincache=dsync modes change
non-synchronous I/O to synchronous I/O, there can be a substantial degradation in throughput for small to
medium size files for most applications. Since the VX_DIRECT and VX_UNBUFFERED advisories do not allow any
caching of data, applications that would normally benefit from caching for reads will usually experience less
degradation with the mincache=dsync mode. mincache=direct and mincache=unbuffered require
significantly less CPU time than buffered I/O.
If performance is more important than data integrity, you can use the mincache=tmpcache mode. The
mincache=tmpcache mode disables special delayed extending write handling, trading off less integrity for
better performance. Unlike the other mincache modes, tmpcache does not flush the file to disk when it is
closed. When the mincache=tmpcache option is used, bad data can appear in a file that was being extended
when a crash occurred.