I am also in the same agreement - though my first reply was bit different - but clarified my stance in the second reply - that's why I love these forums which forces me to read more and more - thank you all .....

ditto for Aran's statement. Keep it simple. You can control your physical disk resources with MS clustering.

Hi,

Welcome to the EMC Support forums

I understand you are referring the some Cluster environment where 2 hosts access the same CLARiiON LUN.

Both the options will work - As per my understanding, the second one is considered as a recommended practice - where each host has a storage group and if you need one LUNs to be shared, add the LUN to multiple storage groups - rather adding multiple hosts to the same storage group.

However, in earlier days we used to create one storage group with multiple hosts for shared LUNs. This is true for NAS (Celerra) Data Movers as well.

I am sure there will be more valuable comments on this thread - others may correct me if needed.

Regards,
Sandip

I agree with you Aran. Thans for replying to my earlier post. The separate Storage group makes sense if the hosts are accessing additional LUNs individually. For a cluster environment, it is quite very common to use single storage group - in fact the Online help page suggests that -

In a cluster environment, you must connect each server in the cluster to the same Storage Group.

However, my earlier response was recollecting some article that I read some time back which I can't recall now.

I just checked the Help page on Rel 26 Navisphere - it is as follows and provides more clarification -

When you connect a server to a Storage Group, the server is:

1) Connected to the Storage group through each server HBA port (initiator) that is connected to the storage system.
In other words, if the server has two HBA ports and each port is connected to one storage-system SP, the server has two connection paths to the Storage Group.

2) Disconnected from any other Storage Group in the storage system to which it is connected.

You can connect multiple servers to the same Storage Group, but the following restrictions apply:

i) The servers must be running the same operating system.

ii) The operating system either supports multiple sharing of the same LUN; has layered software (such as Microsoft Cluster) that supports multiple servers sharing the same LUN.

In a cluster environment, you must connect each server in the cluster to the same Storage Group.

In order to display accurate host/LUN information about a LUN that is shared between servers in a cluster, right-click the shared LUN, and click Update Host Information. Navisphere displays updated information about the server that currently control the shared LUNin the LUN Properties - Hosts tab.

Important For high availability, a server can connect to only one Storage Group per storage system at a time. If you connect a server that already connects to a Storage Group to another Storage Group, the server will disconnect from the first Storage Group. When you disconnect a server from a Storage Group, and then connect it to a different Storage Group, the server can no longer perform I/O to the first Storage Group

Sandip,
It was my understanding that separate SGs were needed only if the hosts needed to access additional LUNs separately apart from the shared LUNs. In all the Microsoft clusters that we deploy we use one SG for both hosts as the hosts only need access to the share LUNs and separate SGs are not necessary to provide that level of access.

Personally the shared SG model is simpler to manage for a cluster. The LUNs and hosts only needed to be added to one SG.

Many thanks for the replies. In our case the second CX3-20 which has the separate storage groups ( one host per SG ) was originally configured for MicroSoft cluster, but is now to be used for Oracle RAC on Linux. There may be a need to have both shared and non-shared LUNS on a host. That being the case, I think we are saying to stay with separate SGs?