That's pretty old information. They're saying that because the original data progression works on a 12 days cycle for "accessible" data. Inaccessible (data that got overwritten but still needs to be around) data would get pushed immediately on next "original" data progression. Also, you are right in that ODDP (flash optimized data progress) is MUCH more quick to move data between tiers especially in Flash. In your WI & RI proposed configuration, you want to size the WI tier for the write changes between the expected Replay schedule OR roughtly 24 hours. You can get the 24hr number from DPACK and divide that by the Replay schedule if  you are taking them more than every 24hrs.   Your thinking is correct here! Also, I would personally go with the single tier option unless you have extremely high write data that necessitates the WI drives. A single tier RI tier is good for "most" customers, but your DPACK data should dictate that.  
Hi, we are considering a SC4020 all flash array. We got a quote with 6x 1.6TB WI and 12x 3.8TB RI TLC. They told us, that the tier 1 should be sized to hold about 12 days of writing data.  What I understand in the white paper "Flash-optimized Data Progression" is, that beginning with SC OS 6.4 the data will be moved to SSD RI tier after every replay taken. So if we take a replay every 4 hours, we do not need such a large tier 1 with WI SSD. Is this correct? And a second question: We got also a quote about a single tier SC4020 with RI SSD only (24x 1.9TB), which fits better in our budget. Is there a reasonable maximum size of daily data to be written? Thanks! 
Considering SC4020 all flash