EMC DPE AND DAE Power Supply Question

Hi Guys

Yesterday I had a good exercise in a customer environment --> Complete power down of the building.

Setup

UPS attached to PDU 1

Public power supply on PDU 2

EMC VNX DPE attached to PDU 1 and PDU 2

DAEs attached to PDU 1 and PDU 2

So we completly cut the power from the public supply:

- Each DAE lost power on one Power supply

- DPE lost power on one Power supply

...... the system run on UPS battery for 30 minutes. After 30 minutes the UPS battery was empty and the DAEs shutdown immediatly the DPE run on its own battery for something like 30 seconds than it shutdown as well.

Before that all ESXi Hosts and its related VMs shutdown before the EMC powered down.

QUESTION

I always though that when you need to powerdown the DPE has to go down first so that no data is accepted anymore. And start the DAEs first so that they are ready for data from the DPE later on.

What we saw in this setup here was that the DAE went down first and than the DPE. In my logic this is bad because maybe the DPE wants to write data and the DAEs are already gone.

Here it did not happen because all the host were down before.

1) Is my first statement true with the correct order for shutdown and power-up?

2) Is our setup wrong or OK?

3) Is there any ways to achieve my goal (dpe shutdown first and than dae) with our setup or another setup?

4) Or is the way it went through just the right way (dae shutdown first and than dpe)?

Thanks