--- Louis  Guillaume <lguillaume@berklee.edu> wrote:

> Hi,
> 
> Sorry for re-posting this. I suspect the previous subject was a little 
> too ambiguous and perhaps it was glossed over on the list.
> 
> Is there any software out there for NetBSD that will allow for 
> abstraction of multiple redundant paths to the same LUNs on multiple 
> Fibre-Channel bus?

I understand what you're looking for, but don't have an answer. Sorry. If
your SAN has a NAS frontend, perhaps you can emulate what you want over
NFS?? Another workaround would be to mirror the two paths, setting one
side of the mirror as read-only (not sure if RAIDfram can handle that).
You won't get complete failover, but it's a start.

To help clarify Louis' situation further, they are looking for something
similar to Veritas Volume Manager's Dual-Multi Pathing (DMP)... Or
Hitachi's Dynamic Link Manager (DLM)... Or EMC's PowerPath... Or Solaris
and AIX's builtin MPIO (Multi-Path IO)... All different names for the same
thing; providing multiple data paths to devices. Anyone who has worked
with fiber-channel, SAN, or multi-initiator SCSI chains should be familiar
with some if not all these products.

Generally how it works is one physical device will show up as two or more
devices on the host, one device file (typically SCSI-like) for each path
the physical device is configured for. It is then up to the multi-pathing
software/driver/whatever to recognize the single device on multiple paths
and combine the paths. With device-driver based products (PowerPath /
DLM), the multiple paths are combined into one virtual device which can be
treated like any other SCSI device. VM software typically does not mess
with the device drivers, rather writing a signature to the disks it sees.
If it sees the same signature across multiple disks, it assumes those
disks must be multipathed and treats them accordingly.

Some OS's such as Solaris (8 and later) and AIX (5.1 and later) have
builtin support. Most OS's do not and rely one one of the other three
products I mentioned above. Native support in NetBSD would be nice, but
convincing EMC, Hitachi, or Veritas to port their software to top 3 or 5
NetBSD platforms would do just as well.

...and apologies if the question has already been answered...

Ed Wensell III
http://www.geocities.com/ewensell3

It is by will alone I set my mind in motion. It is by the Caffeine that thoughts acquire speed - The hands acquire shaking - The shaking become a warning - It is by will alone I set my mind in motion. / Apologies to Frank Herbert


		
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