the screen you posted is related to your OS.it has nothing todo with the RAID controller. After having the server started with the power button, keep pressing F10 for intelligent provisioning menu and after that select Perform maintenance, there you can access to RAID controller configuration.
sdb is dying, as is does not respond to host commandbin a timely manner. However, from what I can understand, sdb really is an array or logical volume/disk, so it does not represent any single disk.
The most probable causes are:
one (or more) physical disk is dying, maybe due to a storm of reallocated sectors. Do your physical disks support TLER? Are they ...
I think you're just misreading the status display in the vSphere client.
If you took the actions to add disks and expand the logical drive, then the hpssacli tool is your source of truth.
And for the vSphere client, it's reflecting the same information, but I bet the column isn't wide enough to show the additional disk numbers :)