This issue means that the specified disk groups do not have IOs during some period of the evaluated time duration, which limits the maximum possible performance on the vSAN cluster. The goals of Max IOPS and Max Throughput require IO activity from each disk group.

Here is a list of possible solutions:

1:If you are running a benchmark, you may increase the number of virtual machines or the number of VMDKs per virtual machine so that all disk groups have some object components.

2:Alternatively, it is possible that your benchmark is not issuing IOs to all the VMDKs that were created.

3:If you do not want to increase the number of virtual machines or the number of VMDKs, you may increase the “Number of disk stripes per object” (the default value is 1) in the Virtual SAN Storage Policy with which the VMDKs were created.

4:You can apply the policy manually to existing or new virtual machines and VMDKs.

To calculate vSAN memory consumption in these releases, use this equation:

BaseConsumption + (NumDiskGroups * (DiskGroupBaseConsumption + (SSDMemOverheadPerGB * SSDSize))) +(NumCapacityDisks * CapacityDiskBaseConsumption)

Where: BaseConsumption: is the fixed amount of memory consumed by vSAN per ESXi host. NumDiskGroups: is the number of disk groups in the host, this value should range from 1 to 5. DiskGroupBaseConsumption: is the fixed amount of memory allocated to each individual disk group in the host. This is mainly used to allocate resources used to support inflight operations on a per disk group level. SSDMemOverheadPerGB: is the amount of memory allocated per GB of SSD. SSDSize: is the size of the SSD disk in GB. NumCapacityDisks: is the number of capacity disks in the host (across all the diskgroups). CapacityDiskBaseConsumption: is the amount of memory allocated per capacity disk.

Constants: BaseConsumption = 5426 MB DiskGroupBaseConsumption = 636 MB SSDMemOverheadPerGB (hydrid) = 8 MB SSDMemOverheadPerGB (allflash) = 14 MB CapacityDiskBaseConsumption= 70 MB

Note: In these releases, encryption and deduplication features have no impact on memory consumption.

Example: One disk group per host, all flash configuration:

BaseConsumption + 
(NumDiskGroups * (DiskGroupBaseConsumption + (SSDMemOverheadPerGB * SSDSize))) +
(NumCapacityDisks * CapacityDiskBaseConsumption)
=
5426 MB + (1 * (636 MB + (14MB * 600))) + (3 * 70 MB)
=
14672 MB

Integration with VUM, VMware Update Manager

vSAN 6.6.1 is fully integrated with VUM to provide a powerful new update process that makes sure your vSAN cluster is up to date.

vSAN Performance Diagnostics:

The feature offers advice such as increasing a stripe width, adding more VMs or bringing more disk groups into use to improve performance. The feature needs the Customer Experience Improvement Program (CEIP) to be enabled, as well as the vSAN Performance Service. Once these have been configured, and the diagnostic information has been gathered for approx. 1 hour, benchmark results can then be examined to see if the maximum number of IOPS, maximum throughtput or minimum latency has been achieved. If not, guidance is provided on how best to achieve these objectives in a benchmark run.



Improved vCenter and unicast behaviour for cluster membership:

If vCenter is down and changes are then made to the cluster, when vCenter recovers, it may reset those cluster changes(UUID ). In vSAN 6.6.1, there is a new property for vSAN called “configuration generation”. This addresses the issue of tracking vSAN membership and will avoid the issue.

New health checks for Update Manager (VUM)
 

The health check has been updated to include checks for new features, such as VUM.