Datastore clusters allow you to pool storage resources. You could think of datastores within a datastore cluster as being similar to hosts in a HA cluster. Like with a HA cluster, there is a form of DRS, called Storage DRS, to help you balance and distribute resources within the datastore cluster. You can set resource management policies at the cluster level which gives you features such as:
- Space Utilization Load Balancing – SDRS can move resources based on free space thresholds set on the cluster.
- I/O Latency Load Balancing – Resources can be moved to alternate datastores in the cluster if certain I/O thresholds are exceeded.
- Anti-affinity rules – You can set rules on the cluster to keep certain virtual disks apart.
Datastore Cluster Requirements
There are a number of requirements to meet before you can create a datastore cluster. These include:
- Enterprise Plus licence
- All hosts linked to the datastore cluster must run ESXi 5.x
- Shared VMFS or NFS volumes
There are also a number of constraints, which include:
- VMFS and NFS datastores can’t be part of the same datastore cluster
- Datastores on SSD storage shouldn’t be included in datastore clusters that have non-SSD disks.
- There is a maximum of 32 datastores per datastore cluster.
Creating A Datastore Cluster
In the Datastores and Datastore Clusters view in the vSphere client, right click the Datacenter object and select ‘New Datastore Cluster’:
On the next screen you will be prompted to choose which level of automation SDRS will use:
It will default to manual mode, which we will keep for the time being. The next screen prompts for the SDRS runtime rules, which includes choosing whether I/O metrics will be used for SDRS recommendations, and setting thresholds for Utilized Space and I/O Latency:
Note that enabling I/O metric inclusion will enable SIOC on all datastores in the cluster. You can also set the following advanced options:
On the next screen you choose the cluster/hosts that will be part of the datastore cluster:
The final step is to choose which datastores will make up the cluster:
The next screen will give you a summary of the options you have chosen. click Finish to create the datastore cluster. Once complete you can administer the datastore cluster in a similar way to how you administer HA clusters. The options and tabs available have a familiar look: