Our production notes include a strong recommendation for MMAPv1 and Azure disk caching:
For all MMAPv1 MongoDB deployments using Azure, you must mount the volume that hosts the mongod instance’s dbPath with the Host Cache Preference READ/WRITE. This applies to all Azure deployments running MMAPv1, using any guest operating system.
The MMAP-specific issue that motivated adding this note does not affect Wired Tiger, but it would be helpful to add some suggestion for the Host Cache setting when using WT. It's not clear if any setting should work or if there is a preferred setting for performance or stability.