Ocfs users - Mar 2004 - OCFS and multipathing

I've got my RAC cluster running pretty smoothly now (thanks again for all
the help so far), but I only have single connections between the servers and
the RAID array.  The servers each have two Qlogic HBAs, and I'd like to find
out if there's any reasonable way to implement multipathing.
 The platform is RHEL 3, and Red Hat's knowledgebase indicates that they
strongly recommend against using the existing multipathing features in the
Qlogic drivers (supposedly some bad failure scenarios are possible).  I'm
also looking at the md driver's multipath capability, but I suspect that it
is not cluster-safe because the md devices have to write some metadata to
the shared disks.
 Is anyone doing real multipathing with RHEL and OCFS?  This is not a top
priority, since the two RAC nodes do provide redundancy, but it would be
tricky to add this capability once the system is in production.

Derek

we are looking at mltipathing for 2.6 which would be rhel4 etc
not at rhel3

rhel3 has mdmpd or something which checks the devices
if you use linear and non persistent superblock, (append devices) you
shouldbe fine. or even just an md per partition wthiout persistent
superblock and use mdmpd 

we haven't really tested that but i dont' see too many problems withthis
,even for clusters

On Sat, Mar 06, 2004 at 09:00:28PM -0800, Derek Suzuki
wrote:
>  I've got my RAC cluster running pretty smoothly now (thanks again for
all
> the help so far), but I only have single connections between the servers
and
> the RAID array.  The servers each have two Qlogic HBAs, and I'd like to
find
> out if there's any reasonable way to implement multipathing.
>  The platform is RHEL 3, and Red Hat's knowledgebase indicates that
they
> strongly recommend against using the existing multipathing features in the
> Qlogic drivers (supposedly some bad failure scenarios are possible). 
I'm
> also looking at the md driver's multipath capability, but I suspect
that it
> is not cluster-safe because the md devices have to write some metadata to
> the shared disks.
>  Is anyone doing real multipathing with RHEL and OCFS?  This is not a top
> priority, since the two RAC nodes do provide redundancy, but it would be
> tricky to add this capability once the system is in production.
> 
> Derek
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