High capacity usage of the vSAN Datastore on target site due to large PSF files for VMs replicated with vSphere Replication

Products

• VMware Live Recovery
• VMware vSAN

Issue/Introduction

•  PSF file (vSphere Replication persistent state file) capacity value for "used capacity" is equal or greater than the size of the base VMDK for VMs replicated using vSphere Replication on vSAN
  
  
• vSAN skyline capacity display screen shows the below:

Environment

• VMware vSAN 
• VMware vSphere Replication
• VMware Live Recovery

Cause

• This is caused when the VM Home Directory Policy is Thick Provisioned
• By default PSF file is deployed with a "Thin" flag.
• The PSF file only contains information of the changed blocks of the disks
• Once the block changes are replicated to the target site, they are discarded and new set of block changes are active - This cycle continues
• This works well on VMFS
• However, in vSAN, the "Thin" flag for the PSF is prevailed over by the Storage Policy of the namespace (VM Home Directory)
• Therefore, whenever a VM is configured for replication, information regarding all the blocks of all the disks are added into the file
• This bloats the PSF file to a huge uncontrollable size.

 

Example:

#esxcli vsan debug object list -u e669b361-8a91-7200-1ced-xxxxxxxxxxxx

structtype:
  ObjectInfo
Health:
  healthy
Object UUID:
  e669b361-8a91-7200-1ced-xxxxxxxxxxxx
Version:
  15
Owner:
  esxi.xxxx.net
Policy:
  stripeWidth: 1
      cacheReservation: 0
      proportionalCapacity: 100 <---------------- meaning all of the capacity assigned to the object is allocated (thick)
      hostFailuresToTolerate: 1
      forceProvisioning: 1
      spbmProfileId: c9eb54d4-c849-4af0-b7b6-xxxxxxxxxxx
      spbmProfileGenerationNumber: 0
      replicaPreference: Performance
      iopsLimit: 0
      checksumDisabled: 0
      CSN: 20183
      SCSN: 17893
      spbmProfileName:  Thick_Policy

Resolution

• This behavior is changed in ESXi 8.0 P05 and above.

Workaround:

• Re-configure the VMs with a Storage Policy "Thin" for the namespace of the VM (VM Home Directory).

 

Additional Information