Running VMware On-Disk Metadata Analyzer (VOMA) on a datastore from Hosts running pre 8.0U3 release where an ESXi 8.0 U3 Host is present in the environment, may incorrectly report corruption related to .unmap.sf file.

Products

• VMware vSphere ESX 8.x

Issue/Introduction

VOMA when run in check mode from a ESXi host pre 8.0U3 release on a volume which is also shared by 8.0U3 ESXi host, user may see false corruptions messages related to .unmap.sf file. 
When VOMA reports a false corruption for .unmap.sf, it reports it for "directory entry (1, 8)" which corresponds with .unmap.sf.
In such case, the log messages logged by VOMA are like what is noted below.

Phase 4: Checking pathname and connectivity.
ON-DISK ERROR: No hash block entry for directory entry (1, 8)
ON-DISK ERROR: Invalid hash idx 15982 type 1, bn 1 sn 8

Cause

In recent versions of VMware vSphere (ESXi) changes were introduced to help control the flow of unmap operations to VMFS datastores. These changes included tracking files, known as "resource files", that exist on-disk within a VMFS datastore but are hidden by default from users. These files do not exist in all cases but can in any environment with 8.0 U3 Hosts present and unmap has been throttled. 
 
In 8.0 U3, a newer type of file is allocated to the datastore to help with unmap throttling - a file with special attributes that are not similar to other files within the datastore, but that will be interpreted in similar ways - leading to VOMA assuming it has found corruption in versions lower than 8.0 U3... even if everything is operating regularly within the Host.

Resolution

Customers are advised to run VOMA from the latest ESXi release in the cluster. This will prevent the issue from happening. To resolve this issue if created, however, we have updated VOMA in vSphere version 8.0 Update 3, and it is equipped to fix any volume which has undergone a VOMA advfix from an older host.

 

Should you receive errors of corruption when querying a host using VOMA, please ensure you are running VOMA from a Host running the latest ESXi version before running an advanced fix on the environment.