As of Rev 1.0 I know of these "bugs"

1. ppdd functions only if the hardware is Intel x86.

2. sparse host files are not supported.
   (if you use dd if=/dev/zero of=ppddfile bs=1k count=xxx
   or if you a real device you will not hit this problem)

3. ppdd and software raid do not work well together. Do not
   put the host file on an "md" device.

4. ppdd and loop do not work well together. Do not put the
   host file on a "loop" device. Do not make a loop file on
   a ppdd device.

5. ppdd and lvm do not work well together. Do not put the
   host file on an "lvm" device. Do not include the ppdd device
   as part of a volume set. 

6. The filesystem you create on the ppdd device must have a block
   size of 1024. The first 1024 bytes must not be used by the
   filesystem - e.g. mke2fs -b1024 works well - other filesystems
   and block sizes are likely to cause problems.
   
