If the physical space on an HDP pool is exhausted, the HDP pool will fail, along with every span that uses it. Therefore, when physical space is low, the server automatically disables filesystem auto-expansion in order to help keep the system serving data.
The span enters this state when the percentage of free physical space plus the percentage threshold set by the span-set-cap-warn-thresh command is below 100. For example, with the capacity warning threshold at 90%, filesystem auto-expansion will be disabled when less than 10% of the physical space is free, and will be re-enabled when more physical free space is provided.
When a span is in this state, the sd-list command's Con column displays LPS (Low Physical Space), to show that auto-expansion is disabled.