vsphere-esxi-vcenter-server-55-storage-guide

Chapter 20 About Virtual Machine Storage PoliciesUnderstanding Virtual Machine Storage PoliciesStorage policies that you define for virtual machines, capture storage characteristics that virtual machinehome files and virtual disks require to run applications within the virtual machine.When you create a storage policy, you can reference storage capabilities advertised by a storage system. Youcan also reference user-defined datastore tags.Although storage policies and storage capabilities have similar semantics, policies describe what usersrequire for their virtual machines, while storage capabilities refer to what the system can offer.You can create several storage policies to define different types and classes of storage requirements.Each storage policy is not only a set of constraints that apply simultaneously. A single policy can includealternative sets of subpolicies, or rule-sets, that represent equally acceptable storage requirements.The virtual machine home files (.vmx, .vmsd, .nvram, .log, and so on) and the virtual disks (.vmdk) can haveseparate storage policies as shown in the following table.Table 20‐1. Example Storage Policy for a Virtual MachineExample Virtual Machine Fileswindows_2008r2_test.vmxwindows_2008r2_test.vmxfwindows_2008r2_test.logwindows_2008r2_test.nvramwindows_2008r2_test.vmemwindows_2008r2_test.vmsdExample for a Storage PolicyStorage Policy 2Example for a Datastore Compliant with theStorage Policydatastore02, datastore05, datastore10windows_2008r2_test.vmdk Storage Policy 3 datastore05windows_2008r2_test_1.vmdk Storage Policy 5 datastore10When you create, clone, or migrate a virtual machine, you can apply the storage policy to the virtualmachine. You can then place the virtual machine to one of the datastores that has capabilities compatiblewith the policy requirements.If you select a datastore that does not match the policy, the Policy shows that the virtual machine is usingnoncompliant storage.About Rule SetsA storage policy includes one or several rule sets that describe requirements for virtual machine storageresources.When you define a storage policy for your virtual machines, you can add one or multiple rule sets, alsocalled subprofiles or subpolicies. A single rule set contains one or several parameters or constrains. Eachparameter describes, in a form of a rule, a specific quality or quantity that needs to be provided by a storageresource. One rule set can include rules from only a single storage provider.To create a policy, one rule set is required, while additional rule sets are optional. Multiple rule sets allow asingle policy to define alternative selection parameters, often from several storage providers.The relationship between all rule sets within a policy is defined by the Boolean operator OR, while therelationship between all rules within a single rule set is defined by AND. Meeting all the rules of any onerule set is sufficient to satisfy the entire policy. Each rule set represents an equally acceptable set ofconstraints.VMware, Inc. 197