Azure Virtual Desktop (AVD) | Scaling plans and Autoscaling

Hi,
We're having a problem with the scaling plan feature.

Facts: We test with 2 identical hostpools, the scaling plan prerequisite (RBAC) are set on subscription level. we use the same scaling plan object for both hostpools.

Hostpool1:
w10Multisession Image created with our cloud based imaging service.
- W10Multisession from azure (21H2) Generation1
- FSLogix und VCRedist uninstalled
- Actual windows Updates installed
- Sysprep sysprep.exe /oobe /generalize /shutdown /mode:vm

Hostpool2:
w10Multisession Image manual created in azure.
- W10Multisession from azure (21H2) Generation1
- Sysprep sysprep.exe /oobe /generalize /shutdown /mode:vm

Testing Scenario: All VM's are down / deallocated
Scaling plan for both hostpools disabled

Problem scenario:
-> Enable scaling plan for hostpool 1
-> wait..... -> No host starts up !! -> checking scaling plan log -> Attached scalingplanlog1.json -> all 3 hosts are marked as
ExcludedSessionHostCount !!

Working scenario:
-> Enable scaling plan for hostpool 2
-> wait..... -> after 5 minutes host starts up !! -> checking scaling plan log -> Attached scalingplanlog2.json -> no hosts are marked as "ExcludedSessionHostCount" !!

Does anybody has this effect od knows in which constellations the scaling plan feature is evaluating session hosts as "ExcludedSessionHost" ?

thanks for your help,

Patrick

scalingplanlog1.json

{
"host_Ring": "R0",
"Level": 4,
"ActivityId": "00000000-0000-0000-0000-000000000000",
"time": "2022-05-03T15:20:21.4366865Z",
"resourceId": "/SUBSCRIPTIONS/00000000-0000-0000-0000-000000000000/RESOURCEGROUPS/P-RG-EDU-TEST-01/PROVIDERS/MICROSOFT.DESKTOPVIRTUALIZATION/SCALINGPLANS/P-SCP-EDU-TEST-02",
"operationName": "ScalingEvaluationSummary",
"category": "Autoscale",
"resultType": "Succeeded",
"level": "Informational",
"correlationId": "8ae9e5b8-c6cb-47ce-943a-923b91c154df",
"properties": {
"Message": "0.00% of session hosts are active (0 of 3 session hosts). This is below the minimum hosts percentage of 20% (1 session hosts). Need to turn on 1 session hosts to meet minimum number of hosts.",
"HostPoolArmPath": "/subscriptions/00000000-0000-0000-0000-000000000000/resourcegroups/p-rg-edu-test-01/providers/microsoft.desktopvirtualization/hostpools/p-vhp-edu-test-01",
"ScalingEvaluationStartTime": "5/3/2022 3:19:33 PM",
"TotalSessionHostCount": "3",
"ExcludedSessionHostCount": "3",
"ActiveSessionHostCount": "0",
"SessionCount": "0",
"NonActiveSessionCount": "0",
"CurrentSessionOccupancyPercent": "NaN",
"CurrentActiveSessionHostsPercent": "0",
"Config.ScheduleName": "weekdays_schedule",
"Config.SchedulePhase": "Peak",
"Config.MaxSessionLimitPerSessionHost": "1",
"Config.CapacityThresholdPercent": "60",
"Config.MinActiveSessionHostsPercent": "20",
"DesiredToScaleSessionHostCount": "1",
"EligibleToScaleSessionHostCount": "0",
"ScalingReasonType": "StartVMs_BelowMinimumActiveSessionHosts",
"BeganForceLogoffOnSessionHostCount": "0",
"BeganDeallocateVmCount": "0",
"BeganStartVmCount": "0",
"TurnedOffDrainModeCount": "0",
"TurnedOnDrainModeCount": "0"
}
}

scalingplanlog2.json


{
"host_Ring": "R0",
"Level": 4,
"ActivityId": "00000000-0000-0000-0000-000000000000",
"time": "2022-05-03T14:18:41.0012950Z",
"resourceId": "/SUBSCRIPTIONS/00000000-0000-0000-0000-000000000000/RESOURCEGROUPS/P-RG-EDU-TEST-01/PROVIDERS/MICROSOFT.DESKTOPVIRTUALIZATION/SCALINGPLANS/P-SCP-EDU-TEST-02",
"operationName": "ScalingEvaluationSummary",
"category": "Autoscale",
"resultType": "Succeeded",
"level": "Informational",
"correlationId": "24ef99f5-650c-4d44-a6ab-1a309f9a1c76",
"properties": {
"Message": "0.00% of session hosts are active (0 of 3 session hosts). This is below the minimum hosts percentage of 20% (1 session hosts). Need to turn on 1 session hosts to meet minimum number of hosts.",
"HostPoolArmPath": "/subscriptions/00000000-0000-0000-0000-000000000000/resourcegroups/p-rg-edu-test-01/providers/microsoft.desktopvirtualization/hostpools/p-vhp-edu-test-01",
"ScalingEvaluationStartTime": "5/3/2022 2:17:52 PM",
"TotalSessionHostCount": "3",
"ExcludedSessionHostCount": "0",
"ActiveSessionHostCount": "0",
"SessionCount": "0",
"NonActiveSessionCount": "0",
"CurrentSessionOccupancyPercent": "NaN",
"CurrentActiveSessionHostsPercent": "0",
"Config.ScheduleName": "weekdays_schedule",
"Config.SchedulePhase": "Peak",
"Config.MaxSessionLimitPerSessionHost": "1",
"Config.CapacityThresholdPercent": "60",
"Config.MinActiveSessionHostsPercent": "20",
"DesiredToScaleSessionHostCount": "1",
"EligibleToScaleSessionHostCount": "1",
"ScalingReasonType": "StartVMs_BelowMinimumActiveSessionHosts",
"BeganForceLogoffOnSessionHostCount": "0",
"BeganDeallocateVmCount": "0",
"BeganStartVmCount": "1",
"TurnedOffDrainModeCount": "0",
"TurnedOnDrainModeCount": "0"
}
}