Dell Powervault ME4 (ME4024): unattended shutdown possible?

I'm rather new in this world of SAN devices/ESXi hypervisors and stuff.

Some years ago we had had physical servers with internal storage connected to a USB/LAN UPS and whenever he had a power loss we would first trigger a clean server shutdown to preserve data integrity and then trigger a UPS shutdown altogether (to preserve UPS batteries). Everything automatically of course.

Now, we are trying to accomplish a similar task on our new setup, comprised from a Dell Powervault ME4024, connected over FC to two physical hosts running ESXi. The entire cluster is protected by an (over-dimensioned) Eaton 93PS 8kVA network-connected UPS. This is also a different beast to what we had back in the day... It can also provide juice for more than an hour in case of power failure.

In any case, we have found out that we can trigger automated shutdowns of the ESXi hosts (including VMs of course). What we are unable to figure out, is how we can trigger a Powervault shutdown at the end of the entire shutdown procedure. Can anyone give some pointers on how to accomplish that in an unattended manner?

Not sure about ME4 but with MD3 and similar storage appliances there's no device shutdown or soft off for that matter. You simply stop I/O (shut down hosts) and when everything is quiet you can remove power.

You might want to use a PDU or connect the ME4 to a separate UPS output group to remove electrical power.

There seems to be command-line facility shutdown to accomplish that via SSH on ME4 systems, check the relevant Dell EMC PowerVault ME4 Series Storage System CLI Guide.

From its help page:

# help shutdown
DESCRIPTION
Shuts down the Storage Controller in a controller module. This ensures that a
proper failover sequence is used, which includes stopping all I/O operations
and writing any data in write cache to disk.

Caution: Performing a shut down will cause data to be unavailable from the
  Storage Controller that is shut down. If the Storage Controller in each
  controller module is shut down, hosts cannot access the system's data.

Perform a shut down before removing a controller module or powering down the
system.

MINIMUM ROLE
manage

INPUT
shutdown
  [a|b|both]

a|b|both
  Optional. Specifies to shut down the Storage Controller in controller A, B,
  or both. If this parameter is omitted, the command affects the controller
  being accessed.
# help shutdown
DESCRIPTION
Shuts down the Storage Controller in a controller module. This ensures that a
proper failover sequence is used, which includes stopping all I/O operations
and writing any data in write cache to disk.

Caution: Performing a shut down will cause data to be unavailable from the
  Storage Controller that is shut down. If the Storage Controller in each
  controller module is shut down, hosts cannot access the system's data.

Perform a shut down before removing a controller module or powering down the
system.

MINIMUM ROLE
manage

INPUT
shutdown
  [a|b|both]

a|b|both
  Optional. Specifies to shut down the Storage Controller in controller A, B,
  or both. If this parameter is omitted, the command affects the controller
  being accessed.

OUTPUT
Messages are displayed when the Storage Controllers are shut down.

EXAMPLE
Shut down the Storage Controller in controller A.

  # shutdown a

RELATED COMMANDS
restart mc
restart sc
show shutdown-status