Mounting VG's on two nodes

[Dave Forber]

I'm not a ServiceGuard pro, so bear with me here please.

We have a two node cluster, with each node running its own instance of Oracle (dbinst1 on node 1 and dbinst2 on node 2). They have a shared disk pool on an external SAN. Node 1 is in charge of the cluster runs the nfs_server package, automatically mounting the disks/VG's/filesystems from the SAN that Oracle needs. In failover, node 2 starts the nfs_server package to mount the filesystems for Oracle. We use the lock disk method to know who has control.

Q. The Oracle techies tell me that at one point, both nodes used to have the filesystems mounted. They could then fire off different queries to different servers. At the moment, only node 1 mounts the shared filesystems. Any pointers?

[melvyn burnard]

Ask them to prove it ! :-]

Perhaps they are confused with Serviceguard OPS Edition vs standard Serviceguard.
Are you running Oracle Parallel Server?

This would need more investigation I suspect.

[Rajeev Shukla]

If its about a filesystem mounted on 2 nodes. Yes it is possible, In one of our setup we have a package in service guard which mounts home directory on 3 servers in the cluster. But the mounts are via NFS.
The node serving the package exports the filesystem which is then mounted on other node.

Other option to mount the filesystem on other node is by activating the VG on other node in Read-Only mode in which they can read the data, fire the queries but cant write.

Cheers
Rajeev

[renarios]

According your case, you have an MC/ServiceGuard failover cluster and not a RAC (Oracle Real Application Cluster)
A VG on an MC/ServiceGuard fail-over cluster can be mounted on two different nodes at the same time. Just take a look in your package control scripts and it might be clear to you.

Hope it helps,

Renarios

[Stephen Doud]

The HP Response Center receives many requests from customers who believe that Serviceguard makes it possible to concurrently mount a file system directly to multiple servers.
Multiply-mounted file systems are not a current feature of HP-UX. The kernel does not have the facility to receive external communication from another kernel to update it's in-core (memory-based) inode table.
Serviceguard OPS or SGeRAC features also do not support shared mounted file systems. Only concurrently accessed -raw- logical volumes are a feature of SG/OPS or SGeRAC.
NFS may make a file system appear to be directly mounted to the unaware.

[Kent Ostby]

Dave --

You cannot currently mount a filesystem on two systems directly.

If you consider the fact that much of the filesystem management is based in memory and that files that are "updated" reside for the most part in memory until written out to disk at a later time, it makes sense why two seperate systems would not be able to share a mounted filesystem directly. I.e. on machine Fred, I update a file but its not on the disk, it's in Fred's memory . On machine Barney, if I try to use that file, I'm using old data .

The only way around this currently is NFS.

Best regards,

Oz