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 files that are currently open 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:
mincache=direct
, mincache=unbuffered
, and mincache=dsync
modes are used in environments where applications are experiencing reliability problems caused by the kernel buffering of I/O and delayed flushing of non-synchronous I/O.
mincache=direct
and mincache=unbuffered
modes guarantee that all non-synchronous I/O requests to files will be handled as if the VX_DIRECT
or VX_UNBUFFERED
caching advisories had been specified.
mincache=dsync
mode guarantees that all non-synchronous I/O requests to files will be 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.
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, 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.