pnfs as a filesystem and for storing
pnfs is a filesystem not designed for storage of
actual files. Instead,
pnfs manages the filesystem hierarchy
and standard meta-data of a UNIX filesystem. In addition, other
applications (as for example dCache) can use it to store
pnfs keeps the complete information in a
pnfs implements an NFS server. All the meta-data can be
accessed with a standard NFS client, like the one in the Linux
kernel. After mounting, normal filesystem operations work
fine. However, IO operations on the actual files in the
will normally result in an error.
As a minimum, the
pnfs filesystem needs to be mounted only by
the server running the dCache core services. In fact, the
pnfs server has to run on the same system. For details see
(has to be written).
pnfs filesystem may also be mounted by clients. This
should be done by
mount -o intr,hard,rw <pnfs-server>:/pnfs /pnfs/<site.de>
(assuming the system is configured as described in the
installation instructions). Users may then access the meta-data
with regular filesystem operations, like ls
-l, and by the
pnfs-specific operations described in
the following sections. The files themselves may then be
accessed with the
dCap protocol (see dCache Book Client Access and Protocols).
pnfs filesystem is not necessary for client
access to the dCache system if URLs are used to refer to
files. In the grid context this is the preferred usage.