5.6.2 vSAN Cluster and Datastore Design
vSAN simplifies the storage configuration because there is only a single datastore for virtual machines. In addition, vSAN uses the concept of objects and components for storage of virtual machine data, where an object consists of multiple components that are distributed across a vSAN cluster, based on the assigned policy for the object.
vSAN 6.2 provides the following different object types:
• VM home namespace – Location for VM configuration and log files.
• VM swap object – Created for the VM swap file (only created when the VM is powered on).
• VMDK – Stores the data that is on a disk.
• Snapshot delta VMDKs – Created for use when a VM has a snapshot created on it.
• Memory object – Created when the snapshot memory option is selected when creating or suspending a virtual machine.
Each object can be a maximum of 255 GB in size. If they are larger, they are split into multiple components. Currently, vSAN 6.2 has a maximum of 9,000 components per host, which can be a limiting factor as to how far it can be scaled. More components are required for larger and more redundant virtual machines.
For instance, one virtual machine with a 500 GB disk (and no snapshots) would always consume the following components:
• Two for VM home namespace (failures to tolerate is always one)
• Two for VM swap objects (assuming that there is less than 255 GB of RAM in the machine)
• Two for the VMDKs (assuming no mirroring and no failures to tolerate)
Therefore, sizing the environment appropriately means that the limit on the number of components can be avoided during the design stage.