Which advantageous have the Raw Device Mapping in VMware?
Raw Device Mappings (RDMs) are really only useful if you have a requirement to have direct access to storage from within your VM. For instance, many application clusters (Microsoft Windows Server Failover Clustering (WSFC), Red Hat High Availability w/SCSI fencing, etc.) need to issue SCSI commands directly to underlying storage. They typically also need to be able to have an exclusive lock on the file system.
In general though, unless you have a specific requirement such as the example above, you should try to avoid using RDMs, since VMDKs on datastores, or storage objects with VVOLs are much more operationally flexible.
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