>Just out of curiousty, how is this different then NFS...
On NFS, what you have is a client-server approach, where the [remote]
server provides access to file data and metadata, and a [local] client
makes that information available to a node. It's a filesystem
independent solution, i.e. it doesn't matter whether or not you're using
linux, bsd, or even something weird as windows on either side [of
course, restrictions to metadata i.e. user/group id information may
If you have let's say 2 servers, you cannot combine them on a single
filesystem, i.e. you have to mount them separated and cannot split a
file between the two transparently.
The NBD solution makes a block device (i.e. a partition on the hard
disk, or the MMC on our concrete case) visible from the network, where
you can have a "client" attached to it on a remote machine and seeing it
as though as it was a local disk. It's a low-level solution, but allows
you to do raid [allowing, among other things, one to see several disks
as being one] or other stuff.
NFS is a higher-level solution, i.e., when properly set, a NFS server
can be shared among several clients, while nbd doesn't provide any such
mechanisms and can be seen as a simpler data packet transport mechanism.
Hope I could show something, I'm not sure whether or not this
explanation is actually clear..