If you enable the "Import data to lowest tier" check box, all data will be ingested at the lowest tier possible. So if you have Tiers 1,2 and 3 and have RAID 10 and RAID 5 on each tier, your new data will be ingested at Tier 3 RAID 5. Once you disable the option, your new data will be ingested at your highest tier (Tier 1 RAID 10 if it is not full). And if you have the fast track option licensed, then it will go to RAID 10 Fast first, then RAID 10 Standard.
We are migrating our vSphere shared storage from an older FC attached SAN to an iSCSI based compellent.  I had built a few LUNs for testing, and now I want to begin vMotioning more VMware guests to the existing compellent LUNs.  When I did my initial move, I had applied a Low Priority (Tier 3) Storage profile to the LUN, and then changed the Storage Profile to Recommended after the vMotion operation was complete.  Now I want to vMotion more guest VMs into the existing Compellent LUNs without the risk of saturating my SSD.  If I select slect the "Import data to lowest tier of storage" option under the advanced properties of the Compellent volume in System Manager and then vMotion the guest to the volume/LUN, will the writes be confined to Tier 3?  Or is the "import data to the lowest storage tier" only really applicable to import operations from an External Device that is setup in System Manager? It is my first Compellent install so I am learning the environment from the ground up. 
Some clarification needed on Compellent Storage tiering