[Unity] Update doc for compressed volume support
@@ -264,6 +264,10 @@ enables compression support needs to be created first:
Then create volume and specify the new created volume type.
+.. note:: In Unity, only All-Flash pools support compressed volume, for the
+ other type of pools, "'compression_support': False" will be
+ returned when getting pool stats.
+
Storage-assisted volume migration support
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