Re: [Xen-users] hostfs for xen?

[Mark Williamson <mark.williamson@xxxxxxxxxxxx>]

> > > Not if my goal is to avoid network filesystems or - like John - to
> > > avoid networking at all! Hostfs is _much_ simpler (and more secure??)
> > > than nfs

In comparison to almost any other Linux filesytem, HostFS is refreshingly 
simple.  It translates VFS ops into host filesystem operations in a rather 
direct way.

Unfortunately it wouldn't be that neat under Xen because you'd have to use a 
"split" (i.e. front and back ends) driver.  The closest thing you could get 
to HostFS in terms of functionality and simplicity would probably be as 
follows:
* "XenHostFS" driver in the guest translates VFS operations to some 
OS-independent format and queues them in an interdomain comms ring
* "XenHostFSd" server in dom0 gets these and translates them into local file 
operations.  This could probably be implemented in userspace if you weren't 
too worried about cunning performance tricks.

> > Actually, modern cifs clients provide unix extensions.  Also, you do not
> > need most of the stuff you suggested.  The advantages of not having that
> > much additional software running in dom0 is true. However, a hostfs is
> > a one-OS solution.  It requires significant engineering to extend to
> > other platforms (like the BSD's, Windows, etc.).  That's something to
> > consider.
>
> True. That may be a no-go argument for a xen-implementation :-(

If the interdomain protocol is well defined then the above implementation 
could be made to work, although each OS would need a different frontend 
filesystem driver.

> They appear to the guest as network drives, but they do not need a samba
> service running on the host. File operations on the host are done by the
> vmware process itself and underlie the fs permissions the vmware process
> owner has. Maybe vmware internally translates that to cifs shares (using
> samba code?).

Ah yes, I think VMWare has an integrated virtual SMB server...  Scary! :-)

Cheers,
Mark

>
> /nils.
>
>
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