HP JFS 3.3 and HP OnLineJFS 3.3 VERITAS File System 3.3 System Administrator's Guide

Chapter 5 97
Performance and Tuning
Choosing Mount Options
mincache
The mincache mode has five suboptions:
• mincache=closesync
• mincache=direct
• mincache=dsync
• mincache=unbuffered
• mincache=tmpcache
NOTE The mincache=direct, mincache=dsync, mincache=unbuffered, and
mincache=tmpcache modes are only available with the HP OnLineJFS
product.
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 should be approximately 15 percent slower than a
standard mode VxFS file system, depending on the workload.
The 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. The 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. The 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
vxfsio(7) for explanations of VX_DIRECT, VX_UNBUFFERED, and
VX_DSYNC. The mincache=direct, mincache=unbuffered, and
mincache=dsync modes also flush file data on close as
mincache=closesync does.