The mincache mode has the following suboptions:
The mincache=closesync mode is useful in desktop environments where users are likely to shut off the power on the machine without halting it first. In this mode, any changes to the file are flushed to disk when the file is closed.
To improve performance, most file systems do not synchronously update data and inode changes to disk. If the system crashes, files that have been updated within the past minute are in danger of losing data. With the mincache=closesync mode, if the system crashes or is switched off, only open files can lose data. A mincache=closesync mode file system could be approximately 15 percent slower than a standard mode VxFS file system, depending on the workload.
The following describes where to use the mincache modes:
The mincache=direct, mincache=unbuffered, and mincache=dsync modes are used in environments where applications have reliability problems caused by the kernel buffering of I/O and delayed flushing of non-synchronous I/O.
The mincache=dsync mode guarantees that all non-synchronous I/O requests to files are handled as if the VX_DSYNC caching advisory had been specified.
Refer to the
vxfsio(7) manual page for explanations of VX_DIRECT, VX_UNBUFFERED, and VX_DSYNC, as well as for the requirements for direct I/O.
The mincache=direct, mincache=unbuffered, and mincache=dsync modes also flush file data on close as mincache=closesync does.
Because the mincache=direct, mincache=unbuffered, and mincache=dsync modes change non-synchronous I/O to synchronous I/O, throughput can substantially degrade for small to medium size files with most applications. Since the VX_DIRECT and VX_UNBUFFERED advisories do not allow any caching of data, applications that normally benefit from caching for reads 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 the file is closed. When the mincache=tmpcache option is used, bad data can appear in a file that was being extended when a crash occurred.