How to enable/disable "Deduplication and Compression" in vSAN and the caveats to consider
Article ID: 426751
Updated On:
Products
Issue/Introduction
This article provides guidance on the requirements and operational implications of enabling or disabling "Deduplication and Compression" within a vSAN environment.
Environment
VMware vSAN OSA (All Versions)
Resolution
VMware vSAN provides a space efficiency feature called "Deduplication and Compression" designed to optimize storage utilization. Enabling or disabling this feature requires a strategic assessment of the current environment prior to enabling/disabling if the cluster is already in production. This is why it's best to enable deduplication and compression prior to putting the cluster into production.
When enabling/disabling "Deduplication and Compression", the setting is configured cluster wide, however the actual changes are implemented within the metadata of the disk group. When enabling/disabling "Deduplication and Compression" on a vSAN OSA cluster, vSAN updates the metadata of each disk group of the cluster one disk group at a time one host at a time. To accomplish this change, vSAN evacuates the data from the disk group, removes the disk group, and recreates it with new metadata that supports "Deduplication and Compression".
The enablement/disablement operation does not require virtual machine migration or DRS. The time required for this operation depends on the number of hosts in the cluster and amount of data that needs to be evacuated per disk group. You can monitor the progress on the Tasks and Events tab in vCenter.
This is why before enabling/disabling "Deduplication and Compression" on a vSAN cluster already in production you need to be mindful of the amount of free space on the vSAN datastore as free space is required to successfully complete the enablement/disablement operation without potentially filling up the vSAN datastore in the process. When a vSAN datastore starts to run out of space this will impact VMs functionality due to low backend storage space.
With clusters configured with the minimum fault domains to meet storage compliance select "Allow reduced availability" to ensure the task completes as vSAN will always try to meet the storage policy compliancy and if their are not enough fault domains to meet compliancy the task won't complete. While objects are in a reduced availability state, they're susceptible going into an inaccessible state if a fault domain goes offline during the enablement/disablement process.
Other considerations before enabling "Deduplication and Compression"
- When a capacity tier disk fails with "Deduplication and Compression" enabled vSAN takes the entire disk group offline. Since "Deduplication and Compression" is managed by the disk group's metadata if a capacity tier disk fails within the disk group to replace this disk you need to remove the disk group from vSAN, replace the failed disk and then recreate the disk group.
- Since "Deduplication and Compression" requires more overhead when committing writes to disk latency sensitive applications, like databases, performance can be impacted. So you wouldn't want "Deduplication and Compression" enabled on clusters that manage latency sensitive applications. Consider using Compression Only for clusters containing this type of workload.
Additional Information
For additional information, refer to the following official documentation:
Feedback
