FAST VP: is tier distribution based on storage pool or LUN?

Hello,

maybe my question is too simple, but I want to be clear on that point before we restructure our data.

Is the distribution between the tiers based on hottnes / coldnes of the storage pool or LUN?

Example (I purposely take two extremes): suppose the current system has one LUN with a SQL server and a datastore for installation media. Now suppose the database is stored on 100% of the EP- and 90% of the P-tier pool capacity, the installation media on 10% P-tier and 20% C-tier pool capacity.

Now, if I create two LUNs and put the SQL server and the installation media each on its own LUN, then FAST VP will try to use 50% of the EP pool capacity for the installation media because some of the data within that LUN is hotter than others? Or does the algorithm consider all the data in the storage pool and the installation media remain on the 10%P-tier and 20% C-tier since the hottnes / coldness within the pool is still the same?

Hope I could make my question clear

Regards,

Dennis