High value of file system Deduplication and/or Compression Overhead observed in the vSAN capacity Overview.
Article ID: 325179
Updated On:
Products
VMware vSAN
Issue/Introduction
Symptoms
For ESXi hosts in a vSAN Cluster with Deduplication and Compression enabled, the Used Capacity Breakdown (Monitor > vSAN > Capacity) for a vSAN cluster displays a large amount of Deduplication and Compression or Compression overhead.
Cause
On a newly created vSAN cluster with Deduplication and Compression or Compression-Only enabled or on a cluster with low capacity utilization, these overheads shows up as a majority contribution in the Used capacity breakdown.
This is because the "Deduplication and Compression Overhead" is determined to be a constant factor (approximately 5.6%) of total raw physical Capacity of vSAN Datastore and should not increase when additional workload is added to the datastore.
For a compression-only enabled cluster the "Compression Overhead" is determined to be a constant factor (approximately ~4.6%) of total raw physical Capacity of vSAN Datastore and should not increase when additional workload is added to the datastore.
This KB is not applicable for cluster where space savings features like Deduplication and Compression are not enabled.
For ESXi hosts in a vSAN Cluster with Deduplication and Compression enabled, the Used Capacity Breakdown (Monitor > vSAN > Capacity) for a vSAN cluster displays a large amount of Deduplication and Compression or Compression overhead.
Cause
On a newly created vSAN cluster with Deduplication and Compression or Compression-Only enabled or on a cluster with low capacity utilization, these overheads shows up as a majority contribution in the Used capacity breakdown.
This is because the "Deduplication and Compression Overhead" is determined to be a constant factor (approximately 5.6%) of total raw physical Capacity of vSAN Datastore and should not increase when additional workload is added to the datastore.
For a compression-only enabled cluster the "Compression Overhead" is determined to be a constant factor (approximately ~4.6%) of total raw physical Capacity of vSAN Datastore and should not increase when additional workload is added to the datastore.
This KB is not applicable for cluster where space savings features like Deduplication and Compression are not enabled.
Environment
VMware vSAN 7.0.x
VMware vSAN 8.0.x
VMware vSAN 6.x
VMware vSAN 8.0.x
VMware vSAN 6.x
Resolution
Pre-allocation of overhead usage for Deduplication and Compression "~5.6%" and Compression-Only "~4.6%" of Total Raw Capacity of the datastore is expected behavior at the time of enabling such space savings feature and will not grow over time-period or with space consumption on Datastore.
Feedback
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