A question always come up before deciding to upgrade the microcode – “Will my servers have access to storage during the upgrade?”. The answer I’ve received from HDS engineers on this is summarised as below:
As long as you have 2 working paths to every connected device (1 from each controller/cluster), then there should be nothing to worry about. Workload on Controllers and Front end ports will need to be below 50% for the duration of the upgrade to prevent any delays with host i/o.
Microcode for USPV is an nonstop scsi online process providing you have multiple paths to all connected hosts/external storage/replicated arrays etc.
The AMS200/500/1000 series will have the microcode upgraded on one controller at a time. Each entire controller including ports will be offline whilst the code is upgraded. This will be done one at a time and once the 1st controller is upgraded and back online, the 2nd controller will then be upgraded.
Hosts will not lose connection to any FAs during the upgrade to the controllers, this is a totally online process (depending on starting code level.
Above information is for guideline only. Check with your HDS support engineer before deciding to upgrade.