In article <x73ecs5dfo.fsf@dailyplanet.wsrcc.com>,
Wolfgang Rupprecht  <wolfgang@wsrcc.com> wrote:
> 1) The flag bits method is not truly heirarchical.  It only allows a
>    2-level storage system.

No, it allows multiple levels.  The vfs layer just doesn't care about
anything other than wether the file is in the top layer or not.  The
actual details of moving files between layers is in a separate daemon. 
The VFS doesn't care where a file is when it's availible; it just needs
to know that it's not so it can ask the hsmd to bring it in.  If it's
there already, it just acts like nullfs.

> 2) The mod-time, size etc. information of the disk and background
>    storage can't both be presented as the same time.

I don't see the problem here. If you want a standard filesystem view of
the file, you use the standard API. If you want gory details, then there
should be an interface to the hsm daemon to query it about stuff like
what level a file resides at, etc.