Hayden,   If you have one pool, and you want to add two different drive technologies (i.e., SAS and SATA) into the same pool, each member would need to be configured with unique raid policy (example: Member_A_SAS is Raid 10, and Member_B_SATA is Raid 50). I agree with Don, IMO run them in seperate pools. Joe 
Hello New to the forums here. I have a PS4000XV with 16 600GB SAS in RAID-10. Users are happy with performance I just need more capacity so I am about to purchase a second member. This environment is growing steadily so rather than add another 3U/3.6TB usable shelf I am exploring the viability of adding a PS4000E with 1TB or 2TB SATA. So my main questions are: 1) Will I slow performance if I mix SAS and SATA in a Pool (I need 2500IOPS < 20ms response) 2) Is anyone actually doing this? (even though Dell tell me the EQL auto-tiers) 3) Assuming it auto-tiers how can I calculate my hot blocks to understand whether I could expect my hot data to fit into my SAS tier (if I understand the tiering correctly)   Thanks in advance for your time to read this. Hayden
Impact of adding a PS4000E to an existing PS4000XV