Follow always the same order for firmware upgrades:

1. first disks DDM
2. second ESM drawers
3. third controllers (at same time NVRAM and controllers)

Controller upgrade can be done On Line unless otherwise stated
All other components require partial downtime
Fail over driver, HBA firmware upgrade require related server downtime
ESM firmware requires stopping IO’s to related EXP
Drive firmware requires stoppins IO’s to related volume group
Risk of data loss if being performed incorrectly