campus cluster with storage replication

Just to add one comment to your plans with respect to controller based replication.

Although support for controller based replication has been integrated into Sun Cluster 3.2 - but for HDS TrueCopy only, there are 2 technical points that you should consider:

1. In a replicated environment you always have one primary, which is in read/write mode, and one or more secondaries, that are in readonly mode - at best. Usually these secondaries are hidden to the OS. I.e. you cannot run any parallel applications, e.g. Oracle RAC in a replicated environment. Except if you use so called cross cabling, i.e. connect every server to both storage subsystems, which is not always practical.

2. In the configuration where you use a single storagebox which is active in the cluster, the outage of that box would trigger a failover with service interruption. This would not happen with host based mirroring, as the volume manager would continue to use the remaining copy of the data.

Now, there are also benefits of using replication technologies: they are usually much better resyncing after a storage box outage. And there might be more.

Regards

Hartmut

HartmutSa at 2007-7-12 20:11:45 >

Hi,

a high level overview with a list of restrictions can be found here:

http://docs.sun.com/app/docs/doc/819-2971/6n57mi28m?q=TrueCopy&a=view

More details how to set this up can be found at:

http://docs.sun.com/app/docs/doc/819-2971/6n57mi28r?a=view

The basic setup would be to have 2 nodes, 2 storageboxes, TrueCopy between the 2 boxes but no crosscabling. The HAStoragePlus resource being part of a service resource group would use a device that had been "cldevice replicate"ed by the administrator. so that the "same" device could be used on both nodes.

I am not sure how a failover is triggered if the primary storage box failed. But due to the "replication" mentioned above, SC knows how to reconfigure the replication in the case of a failover.

Unfortunately, due to lack of HDS storage in my own lab, I was not able to test this setup; so this is all theory.

Regards

Hartmut

PS: Keep in mind, that the only replication technology integrated into SC today is HDS TrueCopy. If you're thinking of doing manual failovers anyway, you could have a look at the Sun Cluster Geographic Edition which is more a disaster recovery like configuration that combines 2 or more clusters and is able to failover resource groups including replication; this product already supports more replication technologies and will even more in the future. Have a look at http://docsview.sfbay.sun.com/app/docs/coll/1191.3

HartmutSa at 2007-7-12 20:11:45 >

Hi,

1. SE6140 replication is currently not integrated with Sun Cluster or Sun Cluster Geographic Edition, but potentially will be (for SC Geo) in the future.

2. Manual DR can be achieved by doing most of the steps manually. Basic setup would be something like:

- 2 clusters, one local, one remote; could be single systems, even without cluster; both clusters/systems setup very similarly, so that in case of a switchover, no basic reconfiguration is needed; i.e. same OS and patch level; very similar volume layout, probably identical for data replication; same change management, to keep users, licenses, installed products, etc in sync.

- determine what to replicate! I would recommend only to replicate data; no OS, no product installation.

- check SE6140 replication setup and procedures needed to switch secondary to primary, reestablish replication etc.

- setup procedures to iport volumes, filesystems, etc.

- setup procedures to start applications

This should give you a very rough idea. I am sure there are steps missing. And, as you can see, it is complex.

Regards

Hartmut

HartmutSa at 2007-7-12 20:11:45 >