Storage Policy Based Management is the lynchpin of VMware Software Defined Storage capability. It provides the ability for a user to define a set of policies, be they based on an SLA and application, workload type or other to be used both at the time of provisioning and the lifetime of the VM to enforce compliance.
Virtual SAN and Virtual Volumes both make use of SPBM and allow capabilities to be configured once and deployed many times and indeed, changed on the fly if and when requirements change. Importantly this is done at the granularity of an object which allows different VMDK’s to have different storage characteristics from eachother or Swap to be different than VMDK’s as an example.
Virtual SAN uses a Default Storage Policy which specifies a few basic rules which are applied to each VSAN object as it is created. In conversation this week I was presented a situation whereby a user wanted to maintain the settings of the Default Storage Policy without adaptation however wanted the ability to set a particular ‘user created’ policy as the default policy used for each newly create VSAN object.
The use case here would to ensure the default VSAN configuration remained largely untouched so in the event of a problem and the defaults could be configured without any delay, however there are also other uses for this. When you have more than 1 VSAN cluster in the vCenter it’s entirely feasible and highly common for these workloads to be different. In this case you may want to define ‘user created’ policy and specify individual defaults and naming to avoid any confusion. In addition, you might have 2 vCenters in Linked Mode both running VSAN Cluster in which case you would have multiple Default VSAN Storage Policies. As the Default Policy cannot be renamed it might be wise to define your own and once again configure defaults at the Datastore layer.
Fig 1 – Multiple Virtual SAN Default Storage Policies
This process is quite easy and is actually possible within the U
- Select a Default VSAN Policy from the Datastore UI
Fig 2 – Assigning Default Datastore Policy
Fig 3 – Selecting ‘user created’ new default policy
Given that there is a 1:1 mapping of SBPM to vCenter Servers and therefore 1 Default VSAN Policy per vCenter, we may need to define our own configuration if we have multiple clusters with different workloads. As each VSAN cluster has a 1:1 mapping to the Datastore it makes more sense for the SPBM to configure the policy at each Datastore. Hopefully this post explains why and how to achieve this.