GEOM Gate.

[Robert Watson]

On Fri, 15 Aug 2003, Pawel Jakub Dawidek wrote:

> On Thu, Aug 14, 2003 at 09:48:57PM +0200, Attila Nagy wrote:
> +> Bruce M Simpson wrote:
> +> >Whatever next? PCI-over-IP?
> +> Collecting cheap on board serial lines to make a big terminal server 
> +> makes sense to me :)
> +> 
> +> BTW, Pawel's stuff would be even more interesting if it would be 
> +> possible to mount the same filesystem on more than one machines.
> 
> It'll be, but probably in read-write mode on one machine and read-only
> mode on rest machines, because you don't export file systems here, but
> disk devices. 

In order to do this, you need a file system capable of multi-node
consistency, and a medium capable of supporting the consistency
mechanisms.  Since we can't handle mounting the same file system
read-write and read-only in multiple places from the same block device
without a likely panic, I expect much the same results with a distributed
block device.  Multiple read-only mounts should work OK, but you don't
want to violate the assumptions of the read-only mounts by introducing a
read-write mount.  File systems can be written that do synchronization on
using a protocol of some sort when talking to a common block device, but
that will keep you busy for a while, I expect :-). 

That said, I think the geom gate stuff looks very cool :-).  You might be
able to run some interesting performance numbers comparing NFS and UFS
over a remote block device.

Robert N M Watson             FreeBSD Core Team, TrustedBSD Projects
robert at fledge.watson.org      Network Associates Laboratories