A: For failover purposes, it might be desirable to have a LUN shared between an active and a standby server, for example, using some type of failover or clustering software. The real question is: Can the LUN be simultaneously used (read/write) by two or more servers and a common application like Oracle and maintain data integrity?

The answer to that question is a qualified "Yes," if you're using volume and/or file synchronization software such as a clustered volume manager, a clustered file system (CFXS), a network file system using NFS or CIFS, or a clustered application like Oracle Real Application Clusters (RAC). Without it, there's no way to coordinate access to changed data blocks and maintain data integrity.

In other words, if you want to have shared access to a group of files or tables, your options are to either use NFS or some type of clustered application/file system.

-- Greg Schulz, senior analyst, Evaluator Group