I have a MacBook Pro running OS X 10.6.5, and would like to disable write-caching (asynchronous I/O) on removable drives so as to help prevent data corruption, but have so far been unsuccessful. Here's what I have tried so far:

- Looked for an Apple-provided setting in System Preferences -- doesn't seem to be anything there.

- Looked for /etc/fstab to change default mount options. /etc/fstab.hd exists, but contains only a comment telling me the file does nothing and should be ignored.

- Found this section in /etc/autofs.conf:

# Mount options.
# A string containing a comma-separated list of mount options
# that will be applied, by default, to all mounts done by automountd(8).
# The options for a particular mount can override these options.
# This controls the same default mount options that the -o option to
# automountd(8) controls.
I tried changing the final line to read:
but even after a reboot, plugging in a drive, and running the "mount" command in the Terminal, the drive was mounted without the noasync option.

- I tried just manually mounting the drive in Terminal with the following command:
sudo mount -o noasync -t hfs /dev/disk1s3 temp
But this gives me the following error:
mount_hfs: -o async: option not supported
This one is particularly baffling, as the -o option I passed in was definitely "noasync", not "async". Also, the man page for mount clearly documents that "async" and "noasync" are both supported options. Why are they not functioning??

I welcome any suggestions. Thanks in advance.