Connecting to logial drives if MS Cluster servers are down?

[BigRich555]

Hi,

Is it possible to connect/map to logical SAN drives is the MS Cluster is down?


Thanks in Advance.

 

[xmsre]

Please explain in more detail. What are you trying to accomplish?


If a LUN exists on a storage device, it's simply a matter of zoning/masking/permissions to connect a host to a LUN. You want to take care to ensure only one host has write acces to a LUN at any given time. MSCS does this by using a SCSI reserve, controlled by the clusdisk.sys driver.

 

[BigRich555]

Thanks for the reply.

The cluster servers are due to be replaced and we have been advised by and external consultant that the we would not need to replace the servers. "All we need to do is configure the client machines to access the SAN logical disk directly."

I guess what I'm asking is this: This is a load of rubbish, but if is possible what are the technical/performance issues.

Cheers

 

[xmsre]

Many storage devices out there can take a pool of storage and present space either via block level protcols (FCP, SCSI, iSCSI) as LUNs or via file level protocols (CIFS or NFS) as file shares. If you are currently presenting a LUN to an MSCS cluster, and the Cluster is in turn presenting shares via CIFS, then at a very high level it is likely possible that you could migrate the data internally on your storage device and present it as CIFS shares to windows hosts (you can generally present a slice as a LUN or a share, but not both for a given allocated piece of storage. Some kind of interally rearrangement of data will likely be required, and probably some vendor services).

MS basically defines the shape of the CIFS standards As new service packs and OS versions come out, now features are continually added. There's generally a lag between when MS releases a feature and when storage vendors add that feature to their products. If you need the latest and greatest features, you'd be better off presenting LUNs to a Windows file server or clustered file server.

Why was it a cluster? If the intent was to provide HA, then does the storage provide the same or better HA? If not, you may consider staying with an MS cluster.

How much does the CIFS license cost on the storage device? Generally it isn't free. Have you done a cost/benefit analysis?

In the end, depending on your specific requirements and the results of your cost/benefit analisys, it could go either way. If you do stay with LUNs presented to a clustered windows file server, migrating is easy. Evict a node, add a new node, rinse and repeat for the other node. The old rolling update.

Just out of curiosity, what is the storage platform?

 

[BigRich555]

Hi

The storage system (IBM SAN (10TB) and 2 W2kAdv Servers (MSSQL2k)) was spec'd to provide HA for files and SQL Databases.

Reading your comments it seems it is techically possible to allow our desktops machines to access the SAN logical drives directly, I just have to work out how!

Thanks again for your input.

 

[xmsre]

If this is an N series, you could carve out some space and present it as CIFS shares. Of course you'd need a CIFS license on the N series. You would then need to migrate the data from the existing cluster (which connects block mode to storage carved from the same device) to the new CIFS shares. When done, remove the old file share resources and disk resources from the MSCS cluster, destroy the old LUNs, and reclaim the space (you'll need some unallocated space on the N series to swing this). You'd likely keep the cluster because you want the host running SQL to connect via block mode protocols to LUNs. If the permissions on the data is fairly simple, you could use robocopy to migrate the data. If it's a more complex permissions structure, you'll probably want to look at something like Scriptlogic's Secure Copy to migrate the data.