You may not have used the maps feature within the VMware Infrastructure Client because large environments become difficult to decipher. The maps view has become an important part of visualizing certain elements of the overall configuration of an ESX environment. One of the more useful mapping views that can help to illustrate relationships is the virtual machine (VM) to datastore map. This shows how many virtual machines are contained in each datastore. It will also show the virtual machines that have connections in multiple datastores.
To use the maps view to show the correlation between VMs and datastores, select the maps button from the main toolbar and then deselect all options except “VM to Datastore”. Then select the datastores, hosts, clusters or resource pools you wish to have represented in the map. It is best to construct your diagram based on the storage configuration. So, if your storage is per datacenter, diagram from the datacenter level down. Once you click the “Apply Relationships” button, a map is drawn based on all of the datastores. You can zoom out of the map by pressing the “-“ key or [ctrl] and scroll on a wheeled mouse. Below is a sample map of a datacenter and the VMs connected to each datastore:
In this example, there are three datastores without a VM assigned within the map. This is the local datastore on the ESX servers in this environment. As a result, it can be quickly determined if a VM is on the local disk. Depending on the environment, locally stored VMs may be prohibited if you use VMotion or certain VMware DRS configurations. This visibility presents an opportunity to see the variance from your standards. For example, lets say I build an environment of Windows Server 2003 VMs with 32 GB of storage assigned. In this example the shared storage resources are in increments of 320 GB, making it so that 9 VMs comfortably fit in each logical unit number which then becomes the datastore through the fiber channel interface, while leaving room for snapshots or .ISO files. If I see a datastore with a very large number of VMs attached, I can easily assume that they are very small. Or, in the situation where a VM is connected to multiple datastores, I can look into why that’s the case if it isn’t the norm. The most common example of a VM attached to multiple datastores is a CD-ROM image mapping to an .ISO image.