The storage policy framework VMware uses in Virtual Volumes and vSAN is the foundation of storage management within...
a VMware infrastructure. VMware Storage Policy-Based Management allows you to use a single control pane as an interface for different data services and storage products.
SPBM enables features such as VM provisioning based on VM storage policies; the advertisement of storage capabilities and data services through vStorage APIs for Storage Awareness (VASA); and communication between the ESXi host, vCenter server and storage arrays.
VMware SPBM storage capabilities
VMware SPBM storage capabilities are usually array-based features and data services that capture storage requirements and can be fulfilled by a storage array. These capabilities provide the user with a better understanding of deduplication, quality of service, array-based snapshots, replication and more.
A VASA provider shows the capability of the underlying storage array through the UI so the administrator can see and use it. The administrator can then create a storage policy by selecting the desired capabilities for the storage array. VASA also makes sure the storage based on the VM storage policy is compliant with requirements.
VM storage policies
VM storage policies are an indispensable component of VMware SPBM for VM provisioning. These policies control how a VM is placed within storage or which type of storage a VM receives. You can define VM storage requirements, such as performance and availability, in vSAN via a VM storage policy. Any time you create a VM, the virtual disk is distributed -- that is, copied to as many nodes as necessary -- across the vSAN data store to meet the storage policy requirements.
With VMware SPBM, any time a VM is created, the storage policy automatically places the VM in a data store that satisfies its storage requirements. To check whether your VMs are compliant with your storage policies, go to Connect via vSphere Client > Hosts and Clusters > Select Your Cluster > VMs in the Storage Policy-Based Management UI.
Storage policy granularity
You can define different storage policies for each VM disk file (VMDK) if one VM has more disk space than another. For example, imagine a VM that has a database running on a separate VMDK. Rather than enforcing a performance storage policy that consumes more storage space on the entire VM, it's better to apply this storage policy strictly to this particular VMDK.
VMware SPBM is useful because it automates administrative tasks. An administrator simply creates a storage policy and selects the VMs to which he wants to apply that policy. The system then automatically recopies different VMs and VMDKs to the data stores that meet the policy's conditions and alerts the administrator if his VMs aren't compliant.
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