The last week-end, I have deployed AzureStack Technical Preview 1 on my lab server that has only SSD. When the deployment was finished, I checked the Storage Spaces and I saw that the available space on each SSD was 31,5GB instead of 512GB.
In Storage Spaces Direct, there is a cache mechanism. This cache mechanism takes all the available space on caching devices (as SATA SSD or NVMe SSD) except 32GB for metadata by default. This cache mechanism can be disabled when enabling Storage Spaces Direct in the Failover Cluster. Moreover, Microsoft indicates that this cache mechanism should be disabled when using only SATA SSD or only NVMe SSD.
So I mounted the MicrosoftAzureStackPoc.vhdx and I edited the CreateFailoverCluster.ps1 script located in AzureStackInstaller\PocFabricInstaller. If you navigate to line 123, you’ll find the command that enables Storage Spaces Direct. So I have changed this line by:
Enable-ClusterS2D -S2DCacheMode Disabled
Then I saved this file in the MicrosoftAzureStackPoc.vhdx. Next I have deployed again the AzureStack Technical Preview 1 from scratch by using the modified MicrosoftAzureStackPoc.vhdx. Once the deployment finished, I check again the storage and this time all is well configured: