[blasdel]

Don't use RAM disks -- it's not 1987, you have a grownup operating system with VM and everything.

As long as you have atimes disabled, the only thing RAM disks will speed up is writes -- recent FS operations are cached in memory automatically (and never paged to disk), so reading a 'warm' file doesn't hit the disk at all.

If you really need such a thing, tmpfs is vastly superior -- it operates directly at the VM page level, instead of idiotically mallocing a ton of address space up front (though I don't think anything like it is available for OS X).