Using an RDBMS for querying tens of Terabytes of time-series data?
Answering this from one point of view: SQL Server 2012 columnstores could easily handle this. I've seen it working and once segment elimination and batch processing kick in, those TBs are reduced to very few actual IOs an the results get churned in few ms (ie. most data is eliminated upfront and there is simply no need to scan 100s of TBs). The queries you asked about are exactly the kind columnstores are designed for. This is such an efficient storage/processing paradigm that there's simply no need for distributed computing, even at hundreds of TB of data.