against a disk as the argument. If you don't it will use a temp file.
The raw disk will use the kernel physio fast path method until the
max number of pending op's is reached then it will queue them. File
system op's are always queued. This is more important with LIO since
operation can get split across and accounting of op's is broken with LIO.
Note that this was broken when locking was added to kqueue (ie. 5.3)
My fix needs to be better integrated with FreeBSD.
Next is an LIO test and implementation.
Sponsored by: IronPort
