Thanks to Don Rye, William Magill, Douglas Thomas, Edward Murphy and
Alan_at_nabeth.
Most people seemed to think this would not be a problem, and I got a few
links/docs which I'll pore over to see further into the issues (attached
below)
However, most convincing was William's comprehensive reply which told me
that what I want is about 6 months ahead of the capability, and that to do
the full three-point fabric will probably be available with the next version
of the HSG controller and DRM software.
Well, I already have a bunch of HSGs and switches, and don't want to spend a
lot more on achieving DR between the three sites. What I can do with the
existing technology is set up two channels each between the sites, but leave
the third leg open. If I can get diverse fibre routing between the sites
that are linked this may give the resilience I need.
I'm also not that keen on the idea of controller based DRM, preferring
host-based mirroring. My feeling is that in a catastrophic failure there's
no real way of knowing where controller replication is in any merge/copy
type operation, whereas host-based is very good at maintaining its own
picture of what data has been written where, and the applications are
ostensibly aware of the I/O status from the OS - I've had surprsingly easy
recovery experiences with both Tru64 LSM mirroring and with VMS Vol
Shadowing. Of course, if I'm completely wrong on this please let me know.
Steve Smith
Links:
http://www.isc-net.upenn.edu/ness/USG/projects/p2000_02_204.html
http://www.compaq.com/products/storageworks/Storage-Management-Software/Data
Docs:
<<Hetrogeneous Open SAN Design.pdf>>
----------------------------------------------------------------------------
---------
Original mails:
> -----Original Message-----
> From: Smith, Steve
> Sent: Monday, February 26, 2001 11:53
> To: 'tru64-unix-managers_at_ornl.gov'
> Subject: More on Triangulating Fibre-Channel
>
>
> Thanks to those who responded so far. I should have made my reasons a
> little clearer.
>
> What I want to do is either replicate, or better, mirror disks between
> sites for DR purposes. This will be done probably using LSM on Tru64 and
> Vol Shadowing on VMS, so I need to put storage at all three sites, and I
> need the servers on each site to be able to see FC paths to each unit.
> Thus if we lose a site, then we boot a server at another site and the data
> is ready and waiting.
>
> The reason for the triangulation, rather than a fan-out topology, is so
> that all servers can reach the storage at all the sites even if one of the
> intra-site links fails.
>
> Steve Smith
>
> -----Original Message-----
> From: Smith, Steve
> Sent: Monday, February 26, 2001 10:09
> To: 'tru64-unix-managers_at_ornl.gov'
> Subject: Triangulating Fibre-Channel
>
> Hi Everyone,
>
> I'm thinking about running Fibre-channel between three sites,
> triangulating between pairs of Compaq Sanswitch-16's. At each site, the
> storage would be connected via HSG80 pairs, to ESA and/or EMA storage
> subsystems, with access from Tru64 machines and probably VMS systems.
>
> I haven't come across a lot in terms of topology for Fibre-channel
> fabrics, like whether and how to do this. But neither have I read
> anything that says we can't.
>
> I'm concerned with how the devices will appear to each Tru64 system
> - will there be problems due to a looping affect round the various paths?
>
> Has anyone attempted to do such a thing, or know where I can get
> hold of enough information to set this up, or not, as the case may be?
>
> It would be useful to get some insight before setting up a testbed.
>
> Thanks,
>
> Steve Smith
> Tel +44 20 7653 7398
> Fax +44 20 7984 0311
>
>
>
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Received on Wed Feb 28 2001 - 18:10:50 NZDT