I had all databases in "recovery pending" not because of disks nor memory. It was from SQL Server upgrade running into an error. The error was caused by 3rd party software had customized SSRS config (non-microsoft tags in rsreportserver.config). I removed the cause, upgraded the database instance, remove the databases (make sure you don't damage all the data and log files), re-attach them back. Violla, they are working again like brand new.