SPBM Policy Exception Cases

vSAN Object Types

There are a number of different object types within VMware vSAN. The most common ones are:

  • 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.
  • vSAN performance Database – This is the database used to store performance information. This usually is rather small, but if set to thick will consume the maximum capacity for a component (255GB + Overhead for RAID protection).
  • vSAN iSCSI volumes – These are stored as VMDKs.
  • Improved Virtual Disks – Previously referred to as Managed Virtual Disks or First Class Disks, these are volumes that contain globally unique UUID and can be used for use cases such as persistent profile volumes, or persistent volumes for containers. They will support VADP making it possible to back them up without an attacked virtual machine.

SPBM policy exceptions

iSCSI home and target objects – Capacity consumed by vSAN iSCSI target namespace objects and home namespace object. The home namespace is created when iSCSI target service is enabled, and the target namespace is created when a new target is created. iSCSI home and target objects

Exception Cases

By default, most objects use the default cluster policy and are configurable, but there are a few exception cases.

VM home namespace – This object will by default follow the policy assigned to the virtual machine unless a specific policy is assigned to the home object. This object will always be a “thin” object with an object space reservation of 0% and will ignore any attempts to make it stored as thick. This makes sense, as this object size is never going to grow significantly and setting a large reservation would waste significant capacity.


VM swap object

Prior to 6.7, this object had a hard-coded value of thick, FTT=1 RAID1. Starting with vSAN 6.2 this was adjustable as an advanced host setting. With vSAN 6.7 this mirrors the VM Home namespace including it’s “always thin” behavior. If

iSCSI home and target objects

The vSAN iSCSI Home and target objects are always thin. Much like the home namespace there is very little capacity used for these configuration files and growth will never be significant.

Snapshot delta VMDKs

The Snapshot objects will mirror the same SPBM policy that is used by VMDK  that the snapshot is attached to. Given the base VMDK would sustain data loss without the snapshot, there is no need to adjust the policy separately from the base VMDK.


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