Announcing: gvirstor

I'm glad to announce availability of GEOM virtual storage class,
(currently) named "gvirstor". The purpose of this class is to enable
creation of huge virtual providers (for example: many terabytes) backed
by limited physical storage, with the expectation that more physical
storage will be added later. This is a part of a logical volume manager,
and provides functionality up to now not available as a native GEOM
class.

gvirstor is currently available either from Perforce (under the name
\\gvirstor) or at http://wiki.freebsd.org/gvirstor in a convenient tbz
archive with appropriate Makefile. Please read the README file packaged
in the archive for instructions on how to build and run gvirstor.

Here are some usage examples from the man page:

 The following example shows how to create a virtual device of default
 size (2 TiB), of default chunk (extent) size (4 MiB), with two physical
 devices for backing storage.

       gvirstor label -v mydata /dev/ad4 /dev/ad6
       newfs /dev/virstor/mydata

 From now on, the virtual device will be available via the
 /dev/virstor/mydata device entry.  To add a new physical device /
 provider to an active virstor device:

       gvirstor add mydata ad8

 This will add physical storage (from ad8) to /dev/virstor/mydata device.
 To see device status information (including how much physical storage is
 still available for the virtual device), use:

       gvirstor list

The latest version of gvirstor is called "beta3" because it has not
received much testing, especially on non-i386 architectures. Please help
by testing both stability and performance of gvirstor if you have
equipment and time.

This work was sponsored by Google with its "Summer of Code 2006"
project, the (very helpful :) ) mentor was Pawel Jakub Dawidek (pjd).