Gil wrote:

So for those of us using other filesystems (e.g. ext2/3), is there
some way to determine whether or not barriers are available?

You'll see something like this in your system log if barriers are not 
supported:

Apr  3 16:44:01 adam kernel: JBD: barrier-based sync failed on md0 - 
disabling barriers


Otherwise, assume that they are. But like Neil said, it shouldn't matter 
to a user whether they are supported or not. Filesystems will work 
correctly either way.

--
Paul