We are trying to scale a vintage VMAX. As far as increasing capacity, it is a real nightmare.

it can grow with disk and controller

Scalability has not been an issue for us. We have about 5,000 users including internal ones, those connecting from the internet, mobile, and other channels. At this point, we don't plan on increasing our usage.

It is scalable. We have 7,000 to 8,000 users. 

For IT, our staff run multiple products, there is no single dedicated person for storage. So there isn't one person dedicated to this solution but rather someone who handles a variety of tasks. 

This product can scale massively given its strong underlying infrastructure.

We did not encounter any issues as we had planned expansion well before its deployment but in an environment where scalability was not planned before deployment, storage bay placement/ordering could cause some issues. New VMAX model (40K) sort out this issue by allowing 25 meters spanning between system and storage bay.

Scalability has dependency on WAN link speed.