@akkartik It varies. Ironically, the best protected will probably be the mid-sized businesses seeking co-location agreements with data centers. Large providers like Facebook or Google will probably collapse in the event of a solar storm of sufficient strength.
The reason for this is that co-location agreements often involve placing servers inside a metal cage. That cage is intended for physical security only. However, it might function well enough as a Faraday cage to prevent solar storm activity from disrupting data on magnetic media. So while power might be disrupted, and perhaps motherboards might get fried as a result of power fluctuations, it is entirely feasible to think that some magnetic and or solid state media will have their contents preserved nonetheless.
Larger businesses, such as Facebook or Google, often own the data centers themselves and therefore don't need metal cages around their server equipment. Therefore, their infrastructure is significantly more exposed.
When I was in the internet service provider industry, small businesses would often seek co-location agreements where space is measured in individual rack units. These racks are frequently metal themselves.
So, I would say the smaller the business, the more likely it would survive a solar flare incident.
A bunch of technomancers in the fediverse. Keep it fairly clean please. This arcology is for all who wash up upon it's digital shore.