VSAN footprint calculation

[lElOUCHE_79]

Hello

I'm trying to find a way to calculate vSAN FOOTprint using a script, I'm not sure if that is possible or not but based on the below formula I guess it's possible

DiskGroupFootprint = DISKGROUP_FIXED_FOOTPRINT + DISKGROUP_SCALABLE_FOOTPRINT + CacheSize * CACHE_DISK_FOOTPRINT + NumCapacityDisks * CAPACITY_DISK_FOOTPRINT

vSANFootprint = HOST_FOOTPRINT + NumDiskGroups * DiskGroupFootprint

PS I asked the same question on vSAN group by mistake and didn't find a way to delete it 

[LucD]

Not sure what you exactly mean by these footprint terms.
Is this something you see in the Web GUI?

[lElOUCHE_79]

Yes, exactly. 

II know that it's maybbe difficult to script it but if there's a formula how to calculate I guess it's possible to get it

[Lalegre]

@lElOUCHE_79,

Thinking out loud, why don´t you use the vSAN Sizer: https://vsansizer.esp.vmware.com/login?returnUrl=%2Fhome.

It will not also provide capacity but will give you an estimate of the memory consumption to get a proper footprint.

[lElOUCHE_79]

@Lalegre

TThank you for the reply, the idea is just to be able to integrate the footprint in my capacity planning script

[LucD]

WHich numbers in the Web GUI are you talking about?

[lElOUCHE_79]

based on this KB https://kb.vmware.com/s/article/2113954 it's the Memory consumed by vSAN

in my capacity planning script I would like to integrate this metric in order to be sure that we are always safe and guarantee resources

[LucD · Accepted solution]

I did some further digging, but as far as I can tell, these data, and their format, are not made public.

Reverse engineering the rvc Ruby sources for the VSAN part (in /opt/vmware/rvc/lib/rvc/modules/vsancmd), I found out they use the QueryVsanStatistics method.

But the labels you have to pass to this method are "The following labels are current supported: - TBD".

With a bit of guess work, and reading the comments in the Ruby source, I could determine that memory statistics are retrieved with the "mem" label.

That indeed returns information, but then the next roadblock is "The details of the counters remain undocumented and unsupported at this point, and this API remains internal."

At that point, I gave up.

I currently have the following, but no documented way to interpret what mem-group-stats and mem-heap-stats contain.
Nor do I know how to interpret the on-esx-collect-duration value

$clusterName = 'cluster'

$cluster = Get-View -ViewType ClusterComputeResource -Filter @{Name=$clusterName}
Get-View -ViewType HostSystem -SearchRoot $cluster.MoRef -PipelineVariable esx |
ForEach-Object -Process {
  $vsanSys = Get-View -Id $esx.configManager.vsanInternalSystem
  $memMetric = $vsanSys.QueryVsanStatistics(@('mem')) | ConvertFrom-Json
  $memMetric.'mem-group-stats' | Out-File -FilePath ".\$($esx.Name)-vsan-mem-group-stats.csv"
  $memMetric.'mem-heap-stats' | Out-File -FilePath ".\$($esx.Name)-vsan-mem-heap-stats.csv"
}

[lElOUCHE_79]

Realy it's very clear and good to know, based on that I think I will not focus on vSAN footprint calculation in my vSAN Capacity planning script

Thank you again