Veritas File System 5.0 AdministratorÆs Guide, HP-UX 11i v3, First Edition, May 2008

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.
The convosync mode
The convosync (convert osync) mode has the following suboptions:
■ convosync=closesync
Note: The convosync=closesync mode converts synchronous and data
synchronous writes to non-synchronous writes and flushes the changes to the
file to disk when the file is closed.
■ convosync=delay
■ convosync=direct
■ convosync=dsync
Note: The convosync=dsync option violates POSIX guarantees for synchronous
I/O.
■ convosync=unbuffered
The convosync=delay mode causes synchronous and data synchronous writes to
be delayed rather than to take effect immediately. No special action is performed
when closing a file. This option effectively cancels any data integrity guarantees
normally provided by opening a file with O_SYNC.
See the open(2), fcntl(2), and vxfsio(7) manual pages.
Warning: Be very careful when using the convosync=closesync or
convosync=delay mode because they actually change synchronous I/O into
non-synchronous I/O. Applications that use synchronous I/O for data reliability
may fail if the system crashes and synchronously written data is lost.
The convosync=dsync mode converts synchronous writes to data synchronous
writes.
As with closesync, the direct, unbuffered, and dsync modes flush changes to
the file to disk when it is closed. These modes can be used to speed up applications
that use synchronous I/O. Many applications that are concerned with data integrity
33VxFS performance: creating, mounting, and tuning file systems
Mounting a VxFS file system