HCI/S2D Reserve capacity - Why is this not just automactic?

@Reeves, Louis There are 2 things you note. Pool reserve space and volume space. When you create a new volume with storage spaces it allocates a fixed amount of space from the storage pool. The reserve capacity of the storage pool is there to allow for a physical disk to fail and be able to start a rapair of the virtual disks (storage spaces/volumes) before the disk is replaced or brought back. You can allocate volumes and fill the stroage pool without a reserve and the only effect is repairs will only take place when the physical disks are all there.

What I believe you are referencing is running out of space on a volume. This is no different on storage spaces as any other disk exposed in Windows Server. The volume has a specific amount of space and if it gets filled up, it's filled until you can extend the volume or reduce the data in the volume. This is not storage spaces specific, any volume on any windows system is the same. There are tools out there that will monitor volume free space. Windows Admin Center in the cluster view, shows volumes and makes clear how much free space is there.

I hope this helps,
StevenEk@Microsoft.com

I also posted the similar question. I just noticed your post- so this is hopefully not going to become common- Hope MS will plan something for this-

https://answers.microsoft.com/en-us/insider/forum/insider_wintp-insider_repair/why-azure-stack-hci-s2d-hcios-reserve-capacity-is/e6be231b-60ac-4463-b171-76c24cf1f78a?tm=1619459006776

Because it's your absolute right to fill up all the space you have. But in that case you need to be able to quickly replace a failed drive...

https://video2.skills-academy.com/en-us/windows-server/failover-clustering/health-service-faults

The following fault should be discoverable via Windows Admin Center, or by the PowerShell for getting faults described in that article. This is the description of the fault that shows:

Pool Capacity (1)
FaultType: Microsoft.Health.FaultType.StoragePool.InsufficientReserveCapacityFault

Severity: Warning  
Reason: "The storage pool does not have the minimum recommended reserve capacity. This may limit your ability to restore data resiliency in the event of drive failure(s)."  
RecommendedAction: "Add additional capacity to the storage pool, or free up capacity. The minimum recommended reserve varies by deployment, but is approximately 2 drives' worth of capacity."

Is there an event in the event logs for this information?