Michael Greenberg wrote:
> Hello again,
> Imagine this scenario: I have two servers connected to the same storage
> array. I got a zpool on the array, and one of the servers "shares" the pool
> to the FC fabric using COMSTAR.
>
> If one machine fails, I imagine the pool can fail over to the other machine
> with Sun Cluster (please bear with my Sun Cluster ignorance - We're a VERITAS
> shop).
>
This is something which has been discussed internally but there are
a lot of details to work out before a fully automated failover between
target nodes can be supported. But I believe it is possible to do so
manually. You need to create to identical configurations of the target
side using the same zpool backend (of course at any given time only one
of the machines can have zpool imported). Keep the stmf service offline
on one of the target and keep it online on the other target (the one
with the zpool). To do the failover, offline the stmf service on the
original target machine, move your zpools to the other target mode
machine and online the stmf service on it.
> But here what I wanted to ask:
> 1. Can a configuration be created on the cluster for the stmf and sbd
> services to fail over the same way the pool does?
> 2. Let's say I got the COMSTAR service configuration syncronized between my
> target machines, can it fail over seamlessly to the nodes using the LUNs?
>
I think the target will failover but the initiator has to retry to
get the I/O going.
> 3. What will happen to the WWNs of the LUNs?
>
The target PWWNs will change. In a multipath configuration this
should not be an issue.
> 4. Or will I have to issue devfsadm to all initiator nodes in the fabric once
> the other machine takes over the pool :( ?
>
If a FC switch is involved, online of stmf service will cause RSCNs
to go to the initiators. This should force a rediscovery. But I have
seen bugs on the initiators where they will drop RSCNs. In which case
some sort of a rediscovery action will be needed.
Sumit
> Any thoughts? Ideas? Technical facts?
> It's just that I don't know well enough how COMSTAR works internally.
>
> Thanks.
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